How to grow pitcher plants? Over-catching insects can cause the plant to die
Pitcher plants look just like a pitcher, complete with a lid, and this remarkable pitcher can even catch insects. If you have one at home, it is a natural insecticide, pollution-free. How do you grow pitcher plants? How to grow pitcher plants: they can tolerate high temperatures of 40°C and low temperatures of -10°C, while northern subspecies are even more cold-tolerant
Pitcher plants look just like a pitcher, complete with a lid, and this remarkable pitcher can even catch insects. If you have one at home, it is a natural insecticide, pollution-free. How do you grow pitcher plants?
How to grow pitcher plants:
They can tolerate high temperatures of 40°C and low temperatures of -10°C, while northern subspecies are even more cold-tolerant, able to endure severe cold of -25°C.
Most carnivorous plants need relatively high air humidity, but the purple pitcher plant needs only 30% humidity, so it is very suitable for growing at home.
From warm, humid swamps to cold, dry barren flats, the purple pitcher plant can grow happily.
1. Pot and soil selection
For planting purple pitcher plants, it is best to use unglazed clay pots, which have good permeability and keep the roots cool in the heat of summer.
Do not use soil that is too fertile as the growing medium, because pitcher plants absorb nutrients by catching insects. If nutrients are sufficient, it will go on strike and stop catching insects.
The soil can be pure sphagnum moss (dried peat moss), or a 1:1 mixture of peat and perlite.
2. Temperature control
To successfully grow pitcher plants, it is very important to understand the temperatures they need. The suitable temperature for purple pitcher plants in summer should be 21-35°C, and in winter 1-7°C is more appropriate.
Pitcher plants are frost-tolerant and do not need to be moved into a greenhouse in winter, except in extreme cold.
3. Watering method
The purple pitcher plant is a wetland carnivorous plant that can grow submerged in swamps year-round in the wild, so it needs an extremely wet environment for vigorous growth.
Under artificial cultivation conditions, if using the water-tray method with a nested pot, when watering you can simply pour water into the outer pot or water until the outer pot is full.
If planting in an ordinary flower pot with drainage, during the vigorous growing season, keep watering once a day and misting to create high-humidity environmental conditions, especially in hot summer,
the number of waterings can be appropriately increased to 2 times, to make up for the rapid evaporation of water by the blazing sun.
4. Light intensity
Purple pitcher plants like sunlight, and can accept direct sunlight as long as the temperature is below 30°C. In spring and autumn, sunlight plus a large day-night temperature difference can turn the pitchers a brilliant purple. If the temperature is too high, it needs to be moved to a spot with bright indirect light.
5. Fertilizing tips
Pitcher plants absorb nutrients through insects, but to make potted pitcher plants grow quickly, regular fertilizing is essential. Generally, during the vigorous growing period, fertilizing should be done once every 3-4 weeks, and the application method can be spraying or drenching, or diluted liquid fertilizer can be
poured into the pitchers for absorption. The fertilizer concentration for pitcher plants is generally 2000-5000 times dilution. Thinner liquid fertilizer is beneficial for rapid absorption by the plant after application, especially when pouring liquid fertilizer into the pitchers, even more attention must be paid to the concentration. Once the winter dormant period arrives, fertilizing can be stopped until warmth returns in the following spring and growth resumes.
6. Pest and disease control
The pests and diseases that harm pitcher plants are mainly caused by the growing environment, such as poor ventilation, too much shade, too cold or too hot conditions, and air pollution. Common pests include red spider mites and aphids. Once discovered, they can be killed by spraying with omethoate or dicofol at 1000 times dilution.
Diseases are mainly root rot caused by sphagnum moss decay. At this time, the pot should be changed promptly, old growing medium removed, rotten roots trimmed, and then replanted with new growing medium. In addition, poor ventilation and excessive shade can easily cause black spot disease. At this time, the environment should be changed, diseased leaves cut off, and then sprayed with chlorothalonil or lime sulfur mixture for control.
The purple pitcher plant's insect-catching efficiency is relatively low, far less than that of the Cape sundew. How many mosquitoes and ants it can catch depends mostly on luck. Generally it can only catch some small flying insects, ants and the like (mosquitoes cannot be caught).
But sometimes when there are too many insects around, the pitchers will wither due to over-catching, so if you are just growing purple pitcher plants for appreciation, when there are many insects, remember to plug the pitcher openings with a ball of cotton.
That is all for the pitcher plant growing methods. Be sure to note that pitcher plants cannot catch too many insects, or the pitcher plant may die.
The Wonder of Turning a Blind Eye - Stories of Chemistry in Everyday Life
The Wonder of Turning a Blind EyeFire and Humanity
The invention of fire dates back to about 500,000 BC. In the cave where Peking Man lived at Zhoukoudian, China, thick layers of ash and some fire-burned animal bone fossils and ash soil were once discovered, proving that they had already learned to use fire.
The use of fire can be said to be humanity's first invention in the history of chemistry. Because humans used fire, they not only had a powerful weapon for defending against wild beasts, but also changed from eating raw food to eating cooked food, shortening the digestion process, thereby promoting physiological changes and development in the human body. Fire is also of great significance to the development of human material civilization. The making of pottery and the smelting of metals are both results of using fire. As for the question of fire, in the late 17th century and early 18th century, due to the rapid development of the European metallurgical industry, chemists were required to explain phenomena such as metal smelting and calcination. Around 1700, the German chemist Stahl and others proposed a theory called the phlogiston theory, believing that all combustible substances contain phlogiston, and that substances that cannot burn lack phlogiston. This erroneous theory dominated the chemical community for nearly a hundred years, hindering people's exploration of the nature of fire, until 1777, when Lavoisier discovered oxygen and completely overturned the phlogiston theory, unveiling the mystery of combustion. Lavoisier submitted a scientific report titled "General Views on Combustion" to the Paris Academy of Sciences, pointing out that combustion can release light and heat, and that the burning of matter is a chemical change occurring between combustible substances and the oxygen in the air. In today's society, combustion is widely used in production and daily life: people use the heat released by combustion to smelt metals; in household life, to boil water, cook, and keep warm; they use the combustion of diesel and gasoline to drive trains, cars, airplanes, and tractors; they use the explosion caused by the rapid combustion of gunpowder to blast mountains and mine, and dig tunnels; in the military, they manufacture bombs, artillery shells, napalm bombs, and flamethrowers to strike invading enemies; and the combustion of the high-energy fuel liquid hydrogen can produce powerful thrust to send giant space rockets into outer space.
Combustion can both benefit humanity and bring disasters to humanity. As everyone knows, combustion can cause fires. In 1987, a catastrophic forest fire in the Greater Khingan Mountains of China burned for 28 days, with the fire area reaching 1.01 million hectares, causing huge losses to the lives and property of the nation and the people. In coal mines, the rapid combustion of gas or coal dust can cause serious explosion accidents. In flour production workshops, fine flour particles floating in the air, when reaching a certain content in the air, can also burn rapidly upon encountering an open flame and cause an explosion.
In large cities with concentrated industry and dense populations, the combustion of fuels such as coal, petroleum products, and natural gas produces air pollutants such as carbon monoxide, sulfur dioxide, nitrogen oxides, and particulate dust, endangering human health.
In daily life, people deal with fire every day. Boiling water and cooking are inseparable from it. However, when using fire, one must pay attention to fire prevention. Neglecting safety, being careless, or lacking fire prevention knowledge may lead to fires, bringing people pain and disaster.
The occurrence of any fire requires three conditions: combustible materials (such as paper, wood, cotton, oil, etc.), combustion-supporting agents (such as air), and ignition sources (such as cigarette butts, embers, etc.). If these three conditions are controlled separately or isolated, a fire cannot occur; if any one of these conditions is removed, a fire will likewise not occur. Every combustible material has its own ignition point and auto-ignition point. For example, the ignition point of wood is generally 250-350°C, and its auto-ignition point is generally around 350°C; the ignition point of cotton is around 150°C, and its auto-ignition point is about 400°C; the ignition point of gasoline is -58 to 10°C, and its auto-ignition point is between 255-530°C; the ignition point of cooking oil is between 140-300°C, and its auto-ignition point is between 350-570°C. If the temperature reaches the ignition point of these combustible materials, they will catch fire upon encountering an open flame. Of course, the lower the ignition point, the easier it is to catch fire; if the temperature reaches the auto-ignition point of a combustible material, it will catch fire even without encountering an open flame. Therefore, the most important measure for fire prevention is to properly store combustible materials, especially to avoid contact with ignition sources.
Water has good fire-extinguishing properties and is the most common, most economical, and most convenient fire-extinguishing agent. Water has a large heat capacity; 1 liter of water rising 1°C can absorb 1 kilocalorie of heat. Therefore, pouring water on ordinary combustible materials such as firewood and wood can rapidly lower the surface temperature of the burning material below its ignition point; at the same time, 1 liter of water, when heated and vaporized, can produce more than 1700 liters of water vapor. Water vapor can dilute the concentration of combustible gases and combustion-supporting gases in the burning zone, and can prevent air from entering the burning zone, thereby extinguishing the fire.
However, not all fires can use water as a fire-extinguishing agent. For example, oil fires and electrical fires. Oil has a lower specific gravity than water and is immiscible with water. When water is poured on burning oil, a splashing phenomenon occurs when cold water meets high heat. The oil floats on the water surface, continues to burn, and overflows with the water flow, expanding the burning area. Water has a certain electrical conductivity. Using a straight water stream to fight electrical equipment fires can cause electric shock injuries.
A simple, easy-to-operate fire extinguisher is called a foam fire extinguisher. It is a cylindrical red steel cylinder with a nozzle, a handle, and a top cover. Inside the cylinder is a sodium bicarbonate solution foaming liquid and a bottle of aluminum sulfate solution, hung on the wall for use. Once a fire occurs, quickly take it down from the wall, carry it to the fire site, turn the extinguisher upside down, point the nozzle at the fire source, and immediately a large amount of foam sprays out to extinguish the fire. Because after the foam fire extinguisher is turned upside down, the sodium bicarbonate solution and aluminum sulfate that were originally stored separately can mix together and undergo the following chemical reaction:
6NaHCO3+AL2（SO4）3=3Na2SO4+2Al（OH）3↓+6CO2↑
After the chemicals in the foam fire extinguisher react, they can produce gelatinous aluminum hydroxide. Under the action of the carbon dioxide produced by the reaction, together with the added foaming agent, it can form a large amount of foam. After these foams are sprayed onto combustible materials, they form a relatively thick foam covering layer on the surface, isolating the combustible material from the air. Therefore, the foam fire extinguisher has a very good fire-extinguishing effect, and is especially unique for extinguishing oil fires.
It is worth noting that before using a foam fire extinguisher, you must check whether the nozzle is unobstructed. If the nozzle is blocked, the foam cannot spray out after turning it upside down, the pressure inside the cylinder increases, and the steel cylinder is at risk of exploding. There are many types of fire extinguishers. Commonly used ones also include dry powder fire extinguishers (the dry powder extinguishing agent can use sodium bicarbonate, ammonium phosphate, or chlorides, etc.), carbon dioxide fire extinguishers (containing solid carbon dioxide), and carbon tetrachloride fire extinguishers (containing carbon tetrachloride liquid), etc. Different extinguishing agents have different fire-extinguishing properties. Therefore, when fighting fires of different natures, corresponding firefighting equipment must be selected. When talking about fire, people naturally think of matches. Small and exquisite matches, strike and they light,
it is the simplest way for people to make fire. Before matches were invented, humans could only obtain fire by drilling wood or by violently striking hard flint (mainly composed of silicon dioxide SiO2) against a small steel knife. It is not hard to imagine how difficult this must have been!
The world's first match was born in Italy more than two hundred years ago. It could be called a giant match, because it was made from a wooden stick more than 1 meter long, with a large lump made of potassium chlorate, sugar, and gum arabic mixed together stuck on one end of the stick. When using it, this large lump was dipped into concentrated sulfuric acid, and it would ignite and burn. This is because after potassium chlorate contacts concentrated sulfuric acid, a chemical reaction occurs, producing a highly reactive substance called chlorine dioxide. Chlorine dioxide reacts with sugar, causing combustion. This kind of match was large and heavy, very inconvenient to carry, required carrying dangerous sulfuric acid at the same time, and was expensive, so it could not be popularized.
By the early 19th century, Swedes discovered friction matches. Friction matches were small, compact, and convenient, and quickly became popular in various countries. This kind of match had sulfur coated on the head, then covered with a mixture of white phosphorus, lead tetroxide or manganese dioxide, and gum. The ignition point of white phosphorus is only 40°C, so it only needed to be rubbed on a wall, tabletop, or shoe sole to ignite. After white phosphorus was lit, with the help of strong oxidizing lead tetroxide or manganese dioxide, the flammable sulfur also burned, and then ignited the small wooden stick.
Although friction matches were convenient to use, they were very unsafe, because once the temperature exceeded 40°C, white phosphorus would spontaneously combust, and white phosphorus is a highly toxic substance. Accidental ingestion of 0.1 gram would cause poisoning and death.
In 1855, the Swede Lundström replaced white phosphorus with red phosphorus and designed and manufactured the world's first box of safety matches. Red phosphorus is non-toxic, and its ignition point is much higher than that of white phosphorus, at 240°C, which made up for the shortcomings of friction matches. He divided the ignition agent into two parts: potassium chlorate and antimony trisulfide were coated on the match head, and red phosphorus, glass powder, and glue were coated on the side of the matchbox. When striking the match, the red phosphorus ignited and then ignited the flammable material on the match head. The matchstick was made of soft wood such as pine or poplar, and the front end was fully soaked with paraffin and rosin, making the matchstick easy to ignite. This kind of match only ignites when rubbed on the matchbox. It is neither toxic nor likely to cause fires, so it is called “safety match”. This kind of match quickly replaced friction matches and sold worldwide, right up to the present.
Matches have been around for more than two hundred years. Over these two hundred years, through continuous improvement by people, many matches with special properties have been manufactured, making the match family increasingly prosperous. Such as windproof matches, welding matches, multi-use matches, and so on.
In daily life, people deal with fire every day. However, when using fire, one must prevent fires. Neglecting safety, being careless, or lacking fire prevention knowledge may lead to fires, bringing people pain and disaster.
The Invention of Saccharin
It is said that during the Chu-Han Contention, Liu Bang's military strategist Zhang Liang sent people to write seven large characters by the Wu River with honey - “Xiang Yu will cut his own throat at the Wu River.” Ants immediately gathered from all directions to feed. When Xiang Yu retreated in defeat to the banks of the Wu River, he saw these striking seven characters formed by many ants and thought that “heaven's will” had run out. He sighed with emotion: “Heaven is destroying me, why should I cross!” With a boat available but refusing to cross, he drew his sword and cut his own throat. This is the story created in Chinese history of “the Han dynasty's realm, gathered by ants,” and also a miracle created by sugar in military history.
Although sugar is a sweetener, it also formed a bond with the mirror-making industry!
In the latter half of the 13th century, Venetians made flat glass. People glued a metal plate behind the flat glass to make a relatively ideal mirror. Things are precious when rare. At that time, mirrors were astonishingly expensive. When Queen Mary Medici of France married, the Republic of Venice gave her a mirror as a gift. The mirror was only the size of a book, but it was worth 150,000 francs!
Later people came up with a method, using mercury (quicksilver) to replace the metal plate. This kind of mirror had very good brightness and low cost, and ordinary people could afford it. However, mercury vapor is toxic. Workers often suffered mercury poisoning accidents when making mirrors, and it claimed the lives of many mirror-making workers every year.
It was not until more than a hundred years ago that people came up with a new method again, using metallic silver to replace mercury mirrors. From then on, mirror-making workers no longer suffered from mercury vapor poisoning.
How are mirrors made? First, select glass without bubbles, grind it flat, wash it clean with alkali, then take silver nitrate and prepare
a solution of a certain concentration, add an appropriate amount of ammonia water, then add an appropriate amount of reducing agent glucose. Pour the prepared solution onto the glass, and the silver nitrate is reduced to metallic silver that deposits on the glass plate, making a mirror. To prevent the silver from darkening and peeling off, finally a layer of paint must be applied to the back of the mirror for protection.
The reaction process of glucose reducing silver nitrate is: AgNO3+3NH3·H2O→[Ag(NH3)2]OH+NH4NO3+2H2O
CH OH(CHOH) CHO + 2[Ag(NH ) ]OH ?heat??
Glucose
CH2OH（CHOH）4COOH+2Ag↓+H2O+4NH3
Gluconic acid This is the famous “silver mirror reaction”. Not only are mirrors silvered this way, thermos bottle inner liners are also
silvered this way. Everyone knows that sugar is sweet. It is a product of photosynthesis in green plants:
Light
6CO2 + 6H 2 O
→
Chlorophyll
C 6 H 12 O 6 + 6O 2
Glucose
Perhaps you do not believe it, but the rags we discard in daily life can also be used to make sugar! More than a hundred years ago, someone conducted an experiment on making sugar from rags, putting rags into sulfuric acid at a concentration of about 70%, heating for a period of time, and the rags disappeared, decomposed into sugar - glucose. So, how do rags turn into glucose?
It turns out that the main component of rags is cellulose. When cellulose is acted upon by acids, that giant molecule splits, forming smaller molecules, and combines with water to become glucose. In chemistry, this is called the “hydrolysis reaction” of cellulose:
（C6 H 10O 5）n + nH 2 O ? ?? nC 6 H 12 O 6
Cellulose Glucose Cellulose is composed of three elements: carbon, hydrogen, and oxygen, and glucose is also composed of three elements: carbon, hydrogen, and oxygen. The difference is that the proportions and arrangements of the three chemical elements in the molecules of the two substances are different.
Since rags can make sugar, then the brothers of rags - wood shavings, rice straw, wheat straw, and many agricultural by-products containing cellulose - can of course also make sugar. Using cellulose hydrolysis to produce glucose has now become a huge industry - the “hydrolysis industry.”
Now, in hydrolysis factories, people first dry and chop some agricultural by-products containing cellulose, then put them into acid-resistant enamel vats, add sulfuric acid (generally at a concentration of 62% or more; if hydrochloric acid is used, the concentration is about 36%), continuously stir and heat, and after 4-5 hours, add water to dilute, then add lime milk to neutralize, and filter. The filtrate at this time is clear but contains impurities and is often brown. Workers add the decolorizing agent activated carbon to the filtrate, and the filtrate immediately becomes colorless and transparent. Next, the filtrate is heated and concentrated, and after cooling, snow-white crystals - glucose - precipitate out.
Sugar is sweet, but there are still many things sweeter than sugar, and edible saccharin is one of them. Speaking of the invention of saccharin, there is also an interesting story! Fahlberg of Russia was a researcher at Johns Hopkins University in the United States and also a chemist,
he busied himself in the laboratory all day. That day, an experiment yielded results, and he happily took out the pencil tucked in his pocket and wrote down the experimental results
in the experiment record. When he put the pencil back into his pocket, he looked at the clock on the wall and saw that it was already 8 o'clock in the evening. He suddenly remembered that today was his birthday, many guests had come to his home, and his wife had especially reminded him that morning to come home earlier in the evening. So he put on his coat and hurried home.
As soon as he entered the door, relatives and friends congratulated him. After a round of greetings, the host and guests took their seats in order, and Fahlberg's wife busily served dishes onto the table. During the meal, a friend asked Fahlberg: “I heard you have recently been researching artificial flavors?” “No, I am doing experiments on aromatic sulfonic acid compounds, it cannot yet be called research.” “What is aromatic...?” “This is a chemical term.” Fahlberg felt he could not explain clearly, so he casually took out from his pocket the pencil he had brought back from the laboratory and wrote the words “aromatic sulfonic acid compounds” on a corner of the newspaper. At this moment, Fahlberg's wife was serving steaming crispy chicken and steak. Fahlberg took the dishes and invited everyone to taste them. Thus, their conversation stopped. “What sweet crispy chicken!” a friend suddenly said. “The fried steak is sweet too,” said another. Fahlberg's wife puzzledly replaced the guests' tableware with new utensils??
Dinner ended, the guests said goodbye, and Mr. and Mrs. Fahlberg sat on the sofa, discussing where that strange sweetness had come from. “I did not add any sugar!” his wife explained. Fahlberg went into the kitchen, licked the tableware the guests had used, then picked up the plates that had held the steak and crispy chicken and licked around the rims. After returning to the sofa, he actually raised both hands, first licking his left hand with his tongue, then his right hand, then took out that pencil from his pocket and licked it with his tongue, and excitedly shouted: “The problem is on the pencil, it is on this pencil!”
It turned out that when Fahlberg tasted the tableware his friend had used, he discovered a sweet spot on the edge of the plate. This was where his fingers had held the plate. And his hands had previously held the pencil used in the laboratory. This showed that the sweetness of the pencil had been picked up in the laboratory.
The next day, at dawn, Fahlberg arrived at his laboratory. He carefully checked the vessels used in the experiment. Full of joy, Fahlberg worked while recording. He said to himself: “This is truly a remarkable invention!”
From then on, Fahlberg concentrated all his energy and devoted himself to researching this topic, and finally extracted a sweet-tasting substance from coal tar - saccharin.
Experiments proved that the sweetness of saccharin is about 500 times that of table sugar. Struggle and hard work finally gave Fahlberg his due reward. In 1879, Fahlberg obtained the patent for inventing saccharin in the United States. In 1886, he moved to Germany and established the world's first saccharin factory in Germany, beginning specialized saccharin production.
Edible Vinegar and Acetic Acid
“Sour, sweet, bitter, spicy, numbing - only sourness lasts the longest.” This saying is true. Speaking of vinegar, it makes people recall some wonderful pleasures. Adding vinegar to cold dishes will make them tasty and make your mouth water endlessly. When cooking shredded pork with fish flavor or sweet and sour spare ribs, adding vinegar enhances color, aroma, and taste, greatly stimulating your appetite and keeping it sharp. A bottle of aged vinegar will add much color to a family's holiday banquet.
As the saying goes, the seven daily necessities are oil, salt, firewood, rice, sauce, vinegar, and tea. It can be seen that vinegar's relationship with people's daily life is extraordinary. And with the development of the organic chemical industry, vinegar has become an important chemical raw material indispensable to human development. Let us now slowly tell the story from ancient times to the present.
In ancient times, vinegar was called xi (xī) cu (cù) or bitter wine, all with the “wine” radical, showing that vinegar and wine have an indissoluble bond. As a condiment, when vinegar began to be used cannot be verified. But among the people there has always been handed down the legend of “Du Kang made wine, his son made vinegar.” It is said that Du Kang's son Heita led his clan to move to the area of Zhenjiang, Jiangsu, and afterward set up a distillery by the river, channeling river water to soak distiller's grains. It was the height of summer, and he fell into a drowsy sleep. Upon waking, following what he remembered from the dream, after 21 days he lifted the cover, and indeed there was a refreshing aroma, sour with a hint of sweetness. Heita then took “twenty-one days” and added a “you” character, calling this sour water “cu” (vinegar). This is the origin of vinegar.
The traditional fermentation method of brewing vinegar has been used to this day. Its key points are: after steaming grains, saccharifying them with wine yeast, and after alcoholic fermentation, the alcohol-containing product obtained is not distilled, then mixed with bran, grain husks, acetic acid yeast, etc., and kept
fermenting at around 40°C to obtain edible vinegar.
Amylase
(C H On + nH O ?starch?powder??enzyme? →nC H O6 10 5 2 6 12 6
Starch Glucose
C H O alcohol-fermenting enzyme? →2C H OH + 2CO
C 2 H 5 OH + O2
Acetic acid bacteria
40 ℃
→CH 3COOH + H 2O
Acetic acid
Edible vinegar, besides acetic acid (containing 5%-6%), also contains a small amount of lactic acid, succinic acid, amino acids, esters, and a certain amount of sugar.
For thousands of years, vinegar has mainly been used as a condiment. And its many functions have made it people's “friend in life.”
The medicinal value of edible vinegar was known to people as early as more than 1700 years ago. Hua Tuo, the famous physician of the Three Kingdoms period, used mashed garlic and half a bowl of vinegar to cure a passing patient, prompting him to vomit out a roundworm and immediately relieving the suffering of a blocked throat that prevented swallowing. 26 years ago, when influenza viruses raged worldwide, causing tens of millions of people to be bedridden, some employees in the photography industry, because they used dilute glacial acetic acid solution when fixing negatives and photos, were spared infection thanks to the disinfecting and sterilizing effect of acetic acid vapor. People thus used acetic acid to prevent influenza. Someone took 5 grams of table salt, stir-fried it over low heat until hot, put in 15 grams of tea leaves and continued stir-frying until slightly scorched, added 200 milliliters of water and boiled, and the resulting filtrate plus 10 milliliters of edible vinegar became a good medicine for treating diarrhea in children. Edible vinegar plays an astringent role here. According to records, edible vinegar also helps digestion, prevents chilblains, reduces inflammation and swelling, and treats psoriasis.
Acetic acid has been used in organic synthesis for more than a hundred years. In 1868, the British scientist Perkin used acetic anhydride and salicylaldehyde to synthesize the flavor vanillin. In 1890, the German chemist Heumann used acetic acid derivatives such as chloroacetic acid as raw materials to synthesize the natural dye indigo. Later, acetic anhydride and salicylic acid were used to synthesize aspirin - a good medicine essential for home and travel. Today's banana oil used in the spray-painting industry is isoamyl acetate obtained by esterification of acetic acid with alcohol.
Film was invented in the 1890s by Edison of the United States and the Lumière brothers of France separately. At that time, when showing films, the greatest fear was burning film and causing a fire, because the film base was made of flammable cellulose nitrate. Cellulose acetate is not easily flammable and does not easily fade. After its introduction, it immediately replaced cellulose nitrate and became an important raw material for photographic negatives and motion picture film.
Acetic acid is the earliest organic acid people prepared, and also the first completely organic synthetic compound scientists produced starting from elemental substances. In 1845, after the German scientist Wöhler artificially synthesized urea from inorganic compounds, the German chemist Kolbe used wood ash, sulfur, chlorine gas, and water as raw materials to synthesize acetic acid for the first time. This laid the foundation for the establishment of organic synthetic chemistry.
The industrial production of acetic acid also developed from the initial methods of distillation of edible vinegar and fractionation of acetic acid from wood dry distillation liquid products (generally 3%-7% of the dry weight of wood) into the current two major production methods.
First, the ethylene oxidation method:
pdCl
·CuC 2
2 1
2CH 2 ? CH 2 ? O 2 ?? ????? 2CH 3CHO
2CH CHO + O
（CH COO） Mn 2CH COOH
3 2 3
70-80 2-3
Second, the direct oxidation method of alkanes:
2CH 3CHO ? 5O2 ?catalyst? 4CH 3COOH ? 2H 2 O heating, pressure In addition to the above two major synthesis methods, scientists believe the most promising production method should be the direct synthesis of acetic acid from methanol and carbon monoxide CH3OH+CO→CH3COOH but this method is still in the exploratory stage because some key technical problems have not yet been completely solved.
Chemistry in Sports
Friends, do you know that in the exciting and visually delightful world of sports, chemical knowledge is everywhere.
For thousands of years, the torch has always been a symbol of light, bravery, and power. Since the 11th Olympic Games, every opening ceremony has held a rather solemn “torch relay.” Who makes the torch flash with dazzling brilliance? It is flammable organic substances. Butane gas and kerosene are both commonly used torch fuels:
2C4H10+13O2 ignite 8CO2↑+10H2O
Butane The novel lightweight torch developed by Chinese chemical experts has a flame about one meter high. Even on a clear daytime, it is still clearly visible from more than two hundred meters away, and it burns brightly even in heavy rain. It added much color to the 11th Beijing Asian Games.
In fiercely contested football matches, we often see players fall on the lawn. At this time the team doctor hurriedly runs forward, uses a small spray bottle, swish! swish! sprays a few times on the injured area of the player, then repeatedly rubs and massages, and before long, the injured player unexpectedly charges back onto the field full of vigor. What miraculous medicine is in the small bottle? This is ethyl chloride (CH3CH2Cl), a colorless, easily volatile organic compound with a boiling point of only
13.1°C. We know that when a liquid volatilizes, it absorbs heat from the surroundings, so when the ethyl chloride medicinal liquid is sprayed on the injured area of an athlete, because it rapidly volatilizes, the temperature of the skin surface drops sharply and sensation is reduced, thereby achieving the unique effects of pain relief and local anesthesia.
At the sports stadium, surrounding the emerald green football field is a ring after ring of very eye-catching brownish-red athletic tracks. This kind of track is laid with the newest synthetic material - plastic. Commonly known as “tartan track.” The structure of the tartan track is like a sponge table tennis paddle with rubber particles attached. The rubber particles on the track surface are like the rubber pips, the plastic surface layer is equivalent to the sponge layer, and the track foundation is like the wooden base plate of the paddle. This kind of tartan track provides a good foundation for track and field athletes to create outstanding results.
Different athletes also have different requirements for the materials of sports shoes. For this reason, designers have used the latest chemical materials to design sports shoes with various properties, which are quite favored by athletes. Basketball and volleyball players need shoes with a certain amount of bounce, so they choose butadiene rubber with very good elasticity for the soles; football players require shoes that can adapt to fast attacks and fast stops and are solid and durable, so they use polyurethane rubber with very high strength as the sole material, and install polyurethane anti-slip studs; track and field athletes require shoes that are soft and full of elasticity, so high-elasticity isoprene rubber soles were designed, satisfying the athletes' requirements.
Why does a white smoke screen appear after the starting gun is fired? The powder in the cap paper contains oxidizing agent potassium chlorate and smoke-producing agent red phosphorus and other substances. The high temperature generated by friction causes potassium chlorate to rapidly undergo a decomposition reaction:
High temperature
2KClO3
2KCl+3O2↑
The oxygen produced immediately undergoes violent combustion with red phosphorus:
4P+5O2Δ 2P2O5
The product of combustion is the white powder phosphorus pentoxide, which easily absorbs water in the air to form acid mist, so the timekeeper sees a faint wisp of white smoke on the black smoke screen.
Before weightlifting, athletes put both hands into a basin containing the white powder “magnesium powder,” then rub their palms together. Is this “magnesium powder” that gives athletes a helping hand really metallic magnesium? Magnesium powder has a silvery-white luster. The true identity of this white powder is magnesium carbonate (MgCO3). MgCO3 has good moisture absorbency and can increase the friction coefficient between the palm and the equipment, enabling athletes to grip the barbell tightly and create outstanding results.
The magnificent gymnasium, decorated with brown glass, is beautiful and elegant, giving people an impression of quiet refinement. Brown glass is a heat-absorbing, heat-insulating glass that can absorb infrared rays. It contains trace amounts of iron, cobalt, selenium, and other oxides, and transmits only 1/4 of the infrared rays that ordinary glass does. Using it to decorate sports buildings not only makes the interior light soft but also has anti-glare and heat-insulating effects. No wonder that walking into a gymnasium on a hot day, one immediately feels elegant and cool.
Chemistry adds splendor to sports and has made great contributions to sports. In the vast world of sports, chemistry is truly everywhere! You see: the sailboard used in surfing is made of foam plastic; bowling balls are pressed from a mixture of hard rubber and plastic; the colorful flying discs are made of plastic; a chemical coating invented by chemists, applied to swimmers' bodies, can reduce water resistance by 10% at a swimming speed of 2 meters per second; a swimsuit composed of ultrafine nylon fiber and polyamide fiber can make athletes swim faster?? However, the abuse of chemical substances has also brought disaster to the pure world of sports. Remember, at the 24th Seoul Olympic Games, the Canadian sprint star Ben Johnson with 9
When he won the 100-meter race in 9.79 seconds against the famous American sprinter Lewis and broke his own men's 100-meter world record, the entire stadium erupted. People shouted his name with excitement, cheering and paying tribute to him as if welcoming a hero. But a few days later, the Olympic Organizing Committee announced a shocking piece of news: Johnson had taken a banned substance during the competition. The new world record he had set was revoked, and his gold medal was taken back. Johnson had deceived international public opinion by improper means and tarnished the Olympic spirit. He was condemned and punished.
Most banned compounds are organic compounds, complex in composition and diverse in kind. At present, the banned drugs stipulated by the International Olympic Committee fall into five major categories and 99 types. They are: synthetic steroids, anesthetics, stimulants, β blockers and diuretics. Among the stimulants taken by athletes, 70% are synthetic steroids.
Taking steroids can build muscle, enhance endurance, help athletes adapt to high-volume training and speed up recovery after training, so that they achieve better results in competition. But such drugs are extremely harmful to the body. They not only damage the liver and are a trigger for liver cancer, but can also cause cancerous changes in the urinary system and bring harm to the heart and blood vessels. To uphold the Olympic principles and protect athletes' health, in 1968 the Olympic Committee announced and completely prohibited athletes from taking banned drugs.
Artificial Rain
As the saying goes: “Fortune is as unpredictable as the weather.” However, with the continuous development of science and technology, this view has become a thing of the past. The wish of humankind for thousands of years to “spread clouds and bring rain” has now become reality. And the scientist who first achieved artificial rainfall was the outstanding American physical chemist Irving · Langmuir.
Irving · Langmuir was born on January 31, 1881, in Brooklyn, New York City, USA. From childhood, Langmuir was extremely interested in natural science and applied technology. When he was young, he had a great ideal: to achieve artificial rainfall and free humankind from the fate of depending on the heavens for food.
Langmuir deeply understood the feelings of farmers hoping for rain during dry seasons. Facing the farmers' eyes pleading for rain and the vast, boundless blue sky, as a scientist he carried out rational and scientific exploration. After in-depth research, he finally figured out the secret.
It turns out that water vapor on the ground rises, meets cold, and condenses into masses, which are “clouds.” The tiny ice points in clouds are only about 0.01 mm in diameter and can float in the air for a long time. When they encounter certain impurity particles (called ice nuclei), they can form small ice crystals. Once ice crystals appear, water vapor will rapidly condense on the surface of the ice crystals, making the small ice crystals grow into snowflakes. Many snowflakes stick together and become snowflakes. When the snowflakes become heavy enough, they roll down from high altitude. This is snowfall. If snowflakes collide with cloud droplets during their fall, the cloud droplets condense on the snowflakes and form opaque ice balls called hail. If snowflakes fall into a warm region with a temperature above 0°C, they melt into water droplets and rain falls.
However, clouds do not necessarily bring rain. This is because ice nuclei in clouds are not abundant and the number of ice crystals is too small.
At that time, a view was popular among people: raindrops use dust particles as “ice crystals,” and if it is to rain, besides water vapor, the air must also contain dust particles. This popular view severely shackled people's experiments and research on artificial rainfall. After all, how easy is it to raise a sky full of dust in cloudy weather?
Langmuir was a scientist with rigorous scholarship who emphasized practice. He was then deputy director of the research laboratory of the General Electric Company in Schenectady, New York State. In his laboratory, artificial clouds were kept, that is, water vapor filling a refrigerator. Langmuir tried every means to make the water vapor in the refrigerator the same as the water vapor in the atmosphere before rain. He also constantly adjusted the temperature and added various kinds of dust to conduct experiments.
One day in mid-July 1946, the sun was blazing and the heat was unbearable. Langmuir was conducting experiments intensively when suddenly the refrigerator stopped cooling due to some equipment failure, and the temperature inside the refrigerator could not drop. He decided to use dry ice to lower the temperature. Solid carbon dioxide has a very large heat of vaporization: 87.2 calories/gram at -60°C. Under normal pressure, it can rapidly transform into gas, absorbing heat from the environment and cooling it, which can lower the surrounding temperature to about -78°C. When he had just put some dry ice into the freezing chamber of the refrigerator, a wondrous scene appeared: small ice particles danced and swirled in the freezing chamber, dense snowflakes fell from above, the whole freezing chamber was piercingly cold, and the artificial cloud turned into ice and snow.
Analyzing this phenomenon, Langmuir realized: dust is not absolutely necessary for rainfall; dry ice has a unique effect in condensing water vapor, namely as cloud ice crystals or ice nuclei serving as “seeds.” Lowering the temperature is also one of the important factors in turning water vapor into rain. He continuously adjusted the amount of dry ice added and changed the temperature, and found that as long as the temperature dropped below minus 40°C, artificial rainfall had a chance of success. The dry ice cloud-seeding method invented by Langmuir was a breakthrough discovery in artificial rainfall research; it broke free from the shackles of old ideas. Interestingly, this breakthrough invention was achieved in a refrigerator in the scorching summer.
Langmuir was determined to put the dry ice cloud-seeding method into practice for artificial rainfall. In 1946, although he was already a 66-year-old man, he still burned with the passion of a young person for exploring the mysteries of nature. One day in 1946, under Langmuir's command, an airplane rose into the sky and flew above the sea of clouds. The test personnel scattered 207 kg of dry ice into the sea of clouds, just as farmers sow seeds in a wheat field. Thirty minutes later, a fierce wind suddenly arose and torrential rain poured down on the earth. The first artificial rainfall experiment was successful.
Langmuir opened a new era of artificial rainfall. Based on the theory of ice crystal nucleation in supercooled cloud layers, scientists also discovered that silver iodide (AgI) and other substances could be used as “seeds” for artificial rainfall. Moreover, in terms of effect, silver iodide is better than dry ice. Silver iodide can be scattered on the ground and, using rising air currents, float up into cloud layers in the sky, making rainfall more simple and easy than with dry ice.
“Artificial rainfall” operations have often been seen in war as a new type of “weather weapon.” During the Vietnam War, the “Ho Chi Minh Trail” from Cambodia to Vietnam was heavy with traffic. Combat materials from abroad supporting the Vietnamese people in resisting the American imperialist aggressors were continuously sent to the front through this only route. But torrential rains and catastrophic floods often occurred there, breaking bridges, destroying dams, and leaving large numbers of transport vehicles struggling on muddy mountain roads. Traffic was greatly affected, and the damage was no less than bombing. At first the Vietnamese side was completely ignorant of this sudden torrential rain. Later, after investigation through many channels, they learned that this was a secret weather operation approved personally by U.S. President Johnson and carried out for 6 years, namely the U.S. conducted an “artificial rainfall” operation over that road.
“The weather can be predicted” means not only “artificial rainfall”; it also inspires people to reasonably carry out artificial weather control. Langmuir also studied this. He hoped that before a storm arrived, it could be eliminated in the bud by artificial control methods. This idea is not only reasonable but also feasible, and it has now been widely applied.
Changing Colors
Our country is one of the world's ancient civilizations. The use of painting pigments also has a long history. From the famous painted pottery excavated at Yangshao Village in Mianchi County, Henan Province, colored patterns of alternating red and black were painted, proving that our ancestors already knew how to use colored pigments for painting more than five thousand years ago. According to textual research, the black pigment used at that time was charcoal powder, and the red pigment was hematite (whose main component is Fe2O3), which the ancients called “red ochre.” Later, people discovered another red pigment in nature, cinnabar, whose color is more brilliant than red ochre. The chemical composition of cinnabar is mercury sulfide (HgS). Because its color is gorgeous and does not fade over time, it has always been highly treasured by painters. The seals stamped on calligraphy and paintings also used seal ink made from cinnabar. In ancient calligraphy and paintings, because of their great age, the paper has discolored and yellowed, but the seals on them are still bright red.
The gracefully dancing flying apsaras in our country's famous Dunhuang murals can be called world art treasures. But the faces and skin of those fairy maidens are mostly gray-black. This is truly strange!
It turns out that the gray-black substance on these paintings is lead sulfide (PbS). But what was originally applied was not lead sulfide, but a famous white pigment, lead white, namely basic lead carbonate. It has very strong covering power, and where it was applied, it could truly be said to be dazzlingly white. Due to long-term corrosion by trace amounts of hydrogen sulfide gas in the air (hydrogen sulfide is produced when coal burns and when animals and plants rot), it gradually changed from white to gray-black.
2PbCO3·Pb（OH）2+3H2S=3PbS↓+2CO2↑+4H2O
(White) (Black) In museums, the oil paintings on display, after a long time, gradually have their white areas become dim and lusterless. The same principle applies. If you encounter this situation, do not worry. Take a soft cloth, dip it in hydrogen peroxide, and gently wipe the surface of the painting, and you can make the painting take on a new look and regain its youth. This is because hydrogen peroxide, which has strong oxidizing properties, can oxidize black lead sulfide into white lead sulfate.
PbS+4H2O2 PbSO4↓+4H2O
(Black) (White) However, in order to preserve the original appearance of ancient cultural relics, we generally do not do this.
The same phenomenon also occurred in art museums in Europe and museums in Italy, where many famous paintings from the Renaissance are treasured. Visitors were surprised to find that in some paintings the sky was not the usual azure blue, but emerald green.
It turns out that the blue pigment used by ancient painters was a mineral called “copper blue,” whose chemical composition is copper sulfide (CuS) and cuprous sulfide (Cu2S). These two sulfides are unstable in nature. Under the action of carbon dioxide and water vapor in the air, over time, they can slowly turn into green basic copper carbonate (CuCO3·Ca(OH)2), and so the “blue sky” gradually became a “green sky.”
An even stranger painting is the huge fresco The Creation of the World, which the master artist Michelangelo spent several years carefully creating. Among this group of rare treasures of murals, one has, in addition to the same endless artistic charm as the other murals, a kind of “special ability”: it can quite accurately predict changes in the weather. Local people discovered that if the pale red at the clothing of the figures in the mural gradually fades and turns into brilliant blue
color, then even if at the time mist curls around and dark clouds fill the sky, one can go out without rain gear at ease; conversely, if the blue at the clothing of the mural figures turns pale red, it indicates that it may rain. Why can this mural forecast the weather? Chemists found the answer to the question. It turns out that among the pigments Michelangelo used, cobalt dichloride was accidentally mixed in. Cobalt dichloride containing crystal water appears red, while anhydrous cobalt dichloride appears blue. Whenever rain is coming, the humidity in the air rises, and the blue anhydrous cobalt chloride in the painting absorbs moisture, forming pale red hydrated cobalt dichloride. When the crystal water in the hydrated cobalt dichloride in the pigment gradually evaporates and returns to blue, it is proof that the air is dry and the weather is about to clear.
proof. Dry or heat
CoCl2·6H2OCoCl2+6H2O Pale red Blue
A British architect added some cobalt dichloride to the cement used for whitewashing exterior walls, ingeniously combining the principle of color change with the principle of color, and created a landscape painting in which the “season” changes with the weather. Whenever autumn is bright and crisp, when the weather is dry, the cobalt dichloride hydrate loses its water and turns from red to blue. Blue and the yellow in the watercolor pigment are complementary and become green, presenting to people the vanished full spring colors. And when spring and summer come, when humidity is greater, cobalt dichloride absorbs moisture again, turns from blue to red. Red and yellow merge into one, and the landscape painting again brings people the orange unique to autumn, symbolizing harvest.
color.
The Application of Color
A Colorful Life
Why is the sky blue? Why are trees green? We live in a colorful nature, and color is a very important part of nature. Color not only affects the lives of almost all animals, but also has a great influence on human life. Imagine if everything around us had only monotonous colors; then you would certainly feel gloomy, depressed, and lifeless. Various colors make everything around us brilliant and colorful, giving people the enjoyment of beauty.
So what exactly is color? Color is actually the final sensation given to our nerves when light of different wavelengths entering our eyes stimulates retinal cells. The wavelengths of light visible to humans range from 400 to 700 nanometers. In the retina there is a type of cone cell containing three basic pigments: red, green, and blue. Light of different wavelengths can activate these pigments, thereby causing nerve excitation and making us perceive these colors. Light with a wavelength of 400 to 500 nanometers can activate the blue pigment and produce the sensation of blue; light with a wavelength of 500 to 600 nanometers can activate the green pigment and produce the sensation of green; light with a wavelength of 600 to 700 nanometers activates the red pigment and produces the sensation of red. All other colors are merely the result of mixing these three basic colors. Mixing all three colors together produces white, and absorbing all three colors produces black.
The ability to distinguish color is not limited to humans. Many fish, amphibians, reptiles, birds, and even insects have the ability to distinguish color, except that their visual range is usually different from that of humans. Only a few animals such as apes and monkeys have the same visual range as humans.
Protective Coloration in the Biological World
Animals often use color to achieve their own purposes, and the most prominent example is protective coloration. Animals often use colors similar to their surroundings to conceal themselves and avoid being discovered by enemies. Animals living in forests can often change the color of their fur with the seasons and with changes in the colors of surrounding plants.
The peppered moth in Britain is an example of adapting to the environment and choosing protective coloration. The specimens of this moth we collected are black under ordinary lighting conditions. Because when British industry began to develop in the 19th century, the fuel burned was mainly coal, and this moth, accustomed to living in the bushes of residential areas, had to rely on black to hide itself in the surrounding soot-laden atmosphere. Against this black background, those light-colored moths were easily discovered and eaten by birds. Now, nearly 90% of the moths in British industrial areas are dark-colored. In recent years, as environmental pollution has been effectively controlled, light-colored moths have now flown back.
However, in nature there are also many animals that are light-colored or even brightly colored. One purpose of these bright colors is to frighten other animals. Poisonous animals or those with unpleasant-tasting flesh often use light or bright colors plus easily recognizable pattern markings to warn carnivorous animals not to eat them. Carnivores then avoid them based on these colors, so the colors benefit both sides. Color also plays an extremely important role when many animals seek mates. Color often has the dual function of frightening enemies and attracting mates. For example, male robins and peacocks use the beautiful colors of their feathers to attract females. It should be pointed out here that in fairy tales and legends circulated among humans and on the stage, beautiful peacocks or other beautifully colored animals are often used to represent pretty girls, while in nature the situation is often the opposite: male animals are generally beautiful and moving, while female animals often appear ugly.
Disguise with color plus pattern is even more effective. Among these, various butterflies are the most prominent. Some butterflies have eye-like patterns on their wings. When they spread their wings and fly, birds or other carnivores are frightened when they see them. Some tropical fish also use bright colors to scare sharks and other “overlords of the sea.” The pale yellow dead leaf butterfly, when its wings are closed, looks very much like a dried leaf and can greatly confuse its enemies. In short, animals have survived precisely by using color to adapt to the environment during the process of evolution.
Humans and Color
The history of humans using color can be traced back 150,000 to 200,000 years, when primitive people smeared red or yellow clay on their bodies to frighten wild beasts and show their beauty to companions. Primitive people also used burned bones and teeth to make black pigments, or ores to make inorganic pigments of other colors. Commonly used were iron ore, copper ore and lead ore, while organic pigments came from animals and plants. White was obtained from chalk and lime; red was taken from the root of madder and the bodies of certain dried female insects (bright red, carmine), and sometimes mercury sulfide was also used. Blue came from copper ore and the plant indigo. Usually these pigment materials were soaked, washed, dried in the sun, and then mixed into oil for use in painting, pottery, or textiles.
There was a pigment called Tyrian purple that was once all the rage in the West. This beautiful red-purple is closely related to indigo. It was prepared from the oxidative secretions of some mollusks in the eastern Mediterranean. It was reported that one (28.4 grams) of this dye required 240,000 marine animals as raw material. In short, this pigment was very expensive, costing about 7,500 dollars per unit. Therefore, people often associated this pigment with nobility. Hence, in English there is the phrase “born to the purple” to mean “of noble birth.” In order to preserve this color that displayed nobility, jealous and suspicious Roman rulers even announced such a cruel decree: “Any person outside the court who wears a purple robe shall be put to death.” This pigment rendered immortal service in establishing the ancient trading center of Phoenicia.
In ancient times, even color carried certain superstitious and religious overtones. The ancient Greeks used colors to represent what they considered the four basic elements: earth (represented by blue), water (represented by green), fire (represented by red), and air (represented by yellow). Heraldry, founded in Germany in the 12th century and later spread to Britain, used colors as specific symbols: golden yellow represented honor, red represented courage, and blue represented loyalty and filial piety. Today, in Western universities, robes with different colored hoods still represent a person's specific academic status. In ancient China, emperors used bright yellow to represent their supreme power.
Modern scientific research tells us that color produces certain psychological effects on people: white is quiet, black is silent, red is passionate, green is cool. Moreover, color can also give people a sense of taste. People always feel that yellow is sweet, green is sour, brown is bitter, and red is salty. People even use this effect of color to treat illnesses: a light blue environment has an antipyretic effect on patients with high fever, a purple environment can make pregnant women feel comforted, and an ochre-colored environment helps patients with low blood pressure raise their blood pressure; while blue and white environments can lower blood pressure in patients with high blood pressure; yellow and red environments can promote blood circulation. If patients stay in rooms mainly in green, light blue, or beige, they can recover health faster. Red can make a person's pulse beat faster, while blue makes the pulse beat slower. Blue or green food and environments can reduce a person's appetite, while yellow or orange can increase appetite. Based on the above characteristics, people can paint different colors in different environments to make people feel more comfortable in such environments.
The first person to make synthetic dyes was the Englishman William · Henry · Perkin. As early as 1856 or earlier, he proposed the idea of making synthetic dyes, when natural alizarin and indigo still dominated the market. These pigments required large quantities of natural plants to produce and could no longer meet the needs of industrial development at that time. Only 18 years old, Perkin tried to synthesize quinine in a small hut in his backyard. When he mixed aniline sulfate with dichromate, he obtained a red-purple product, aniline purple. In fact, this dye was a group of compounds with similar structures. From then on, synthetic dyes developed rapidly, among which the most important were picric acid, fuchsin, and rosolic acid. Today, synthetic dyes have become an important chemical product widely used in the textile, papermaking, soap and detergent, and plastics industries. Color makes the world around us gorgeous and varied, and makes our lives rich and colorful. Once we understand the principles of color formation and how to synthesize various dyes and pigments, we can more consciously beautify our environment and produce more dyes of excellent quality and bright color, making our work more efficient,
our lives more comfortable, and our spirits more joyful.
A Special Chemical Sense Organ: Smell
Smell in the Biological World
More than 20 years ago, a strange thing happened in California, USA: in a fish pen used for raising fry, a salmon 35 decimeters long and weighing 0.5 kg was unexpectedly found. These fish usually live in the cold waters deep in the Pacific Ocean. What is astonishing is that the only connection between this fish pen and the external waters was a labyrinth-like outlet pipe, with a 75 cm high fence and wire mesh in between. People simply could not imagine how this indomitable “warrior” had gone through all kinds of dangers and crossed all obstacles to arrive here. In order to commend its glorious achievement, people erected a 5-ton redwood statue beside the fish pond for later generations to admire. What exactly navigated it on this long and winding journey? After carefully studying the migratory habits of salmon, people learned that young salmon live in streams. The geological environment of the areas through which each stream flows is different, and the aquatic plants in the stream and the plants growing along the banks near the water are also different, thus making the smell of each stream different. These smells pass through the fish's nostrils and leave strong marks at the olfactory bulb in its head, lasting a long time. Therefore, adult salmon living in the deep sea still rely on this memory to cleave through waves and spare no hardship to return to their hometown.
The catfish is a blind fish with a sensitive sense of smell. Long-term life in turbid water has made it nearly blind, but it can rely on smell to find food for itself without difficulty. The catfish's sense of smell also controls its gregarious life; it can judge the identity, age, sex, and species of others through smell. Because of the role of smell, one can often see large numbers of catfish crowded into a limited area without fighting one another.
Like fish, insects, reptiles, and even advanced mammals rely mainly on smell among the many pieces of information around them, and sometimes odor is even used by animals as a means of communication. Therefore, for many animals, smell is the key to their lives.
Among reptiles there is a kind of blind snake that can track ants by the smell they leave and go to ant nests to hunt ants. At the same time, it also secretes a scented substance itself. This smell has several functions: dealing with worker ants that might attack it; warning other insect-eating snakes that this ant nest now belongs to me, so do not come to snatch food; and it can also use this smell to find its own companions.
Mammals also have sensitive smell. Many animals rely on scent to find food, or use smell to detect enemy beasts and escape in time. Especially those herbivorous animals generally do not have very good eyesight. Therefore, in finding food and preventing enemy beasts, they rely even more on their keen sense of smell. Some mammals, like the blind snake, leave special smells on shrubs and grass in their living areas as markers. This is equivalent to issuing a notice to animals of the same species: this place has been occupied. Thus fights over territory are avoided. These smells are usually emitted by animal urine or animal endocrine glands. For example, antelopes, musk deer, and [omitted in source] have this kind of special secretory gland.
The dog's sense of smell is astonishingly acute. According to research, the nasal cavity of a sheepdog contains 22 million olfactory cells, covering an area of 120 cm2, while the human nasal cavity has only 500,000 olfactory cells, covering an area of only
6.25 cm2. No wonder that compared with a dog's olfactory ability, humans are far behind. Therefore, people understood very early how to train dogs to track criminals' trails. A dog can, several hours after a case occurs, rely on the smell left by the criminal to track him for several kilometers or even dozens of kilometers and catch him.
Lower animals such as insects depend even more strongly on chemical information for survival. For example, when some insects are threatened or attacked by intruders, they can release a chemical substance to raise an alarm, notifying companions in the nest to be on guard and summoning them to defend themselves. These chemical substances are easily volatile. Insect death is also announced by the smell of chemical substances: when the corpse of a dead ant decomposes, it releases a special substance that can be recognized by other ants.
The role of a kind of sex pheromone in insects is even more miraculous. For example, the queen bee secretes a sex pheromone: 9-keto-α-nonenoic acid (also called 9-oxo-2- + -carbenedioic acid). Its smell can prevent ordinary worker bees from developing into queen bees. In termite colonies, the termite king can also secrete some similar substances, hindering worker termites from developing into kings. The sexual behavior of insects is even more deeply influenced by sex pheromones. The sensitivity of male moths to female moth sex pheromones is astonishing: it can detect a female moth 2 kilometers away. Such high sensitivity cannot be achieved by any of humans' various analytical instruments.
For the highest organism, humans, smell seems less important than it is for lower animals. The sensitivity of smell is also far inferior to that of some lower animals. But compared with the sensitivity of other sensory organs, smell is still second to none. People can smell certain odors in the air at concentrations of only 1-10-7 ppm (one part per million is 1 ppm). Such trace amounts of substances cannot be seen at all by eyes that are “keen enough to detect the minutest detail.” Therefore, many trace substances cannot be seen or touched, but we can discover their existence by smell. Some hunting peoples, such as the Bushmen of South Africa and the Australian Aborigines, still use their keen sense of smell to discover and track wild beasts.
Human secretions also contain various chemical substances that can stimulate the sense of smell in animals or humans. The main odor in human sweat is butyric acid (CH3-CH2-CH2-COOH). If 1% butyric acid in sweat penetrates into the sole of a shoe, each footprint can leave at least 2×1011 molecules of butyric acid. These molecules are 100 times the minimum threshold of human smell. Originally humans should be able to smell them, but because habit reduces the efficiency of smell for this butyric acid, most people cannot smell the odor of human sweat. In addition, due to differences in people's living habits, age, sex, diet, living environment, and metabolic functions, the composition of the various chemical substances secreted also differs. A dog with a keen sense of smell can distinguish each person's different odor and tell which is its owner and which is the criminal to be pursued. The odors volatilized by steroidal hormones, lysine, lactic acid, and other substances in human sweat attract mosquitoes. Some doctors can even diagnose diseases by smell based on the connection between certain odors and diseases. For example: distinguishing the scent of apples is characteristic of patients with diabetic acidosis; a person whose body gives off the yeast smell of freshly baked black bread indicates typhoid fever; patients with schizophrenia often emit a strong human body fragrance during the critical period of their illness, and psychopathologists use this odor as a basis for judging the patient's condition.
Characteristics of Smell
As early as more than two thousand years ago, people had already begun to study the language of smell. The ancient Roman philosopher
Lucretius proposed that pleasant odors are the result of smooth, round “atoms,” while “rough” odors are caused by “barbed” atoms. For two thousand years this view did not fundamentally change. In 1756 the famous Swedish taxonomist Linnaeus proposed 7 basic odor classes, and later people proposed even more classification levels. Amoore collected various data on many odors, including odors that humans cannot smell, and divided them into 62 chemical categories. He believed such classification was superfluous. For humans, there are only 20-30 primary odors. At present, the theory accepted by most people is probably the stereochemical theory proposed by the Western Regional Research Laboratory of the U.S. Department of Agriculture. This theory points out that sensory organs are basically adapted to the shape and volume of gas molecules, that is, only when gas molecules of a certain geometric shape fit the special shape of the sensory organ can smell be produced. It is like only one kind of stopper fitting tightly into one caliber of bottle. According to this theory, each sensory organ must correspond to one primary odor, which is obviously impossible. Therefore, although this theory can explain many phenomena, it is still questioned by people.
Researchers have found that smell is more sensitive than taste both in perception and in discrimination. Because animals often use odor as an early warning message, they are especially sensitive to it. People doing chemical experiments can smell the odor of a certain substance even if there is only 10-14 grams of the gas, which is far lower than the limit that laboratory instruments can detect.
Now it is generally believed that for a substance to have an odor, it must meet two conditions: first, the substance is volatile and can release its molecules into the air. Second, it must be slightly soluble in water, so that it can pass through the mucous membrane covering the olfactory sensory organs. Some people also suggest that these substances must also be soluble in lipids, so that they can pass through the lipid cell membranes of the sensory organs. The various odors we can usually smell, such as hydrogen sulfide (H2S) from rotten eggs, the smell of ammonia water (NH3·H2O), and the fragrances of various fruits - banana-scented n-butyl acetate (CH3COOC4H9), pear-scented isoamyl acetate (CH3COOC5-H11); pineapple-scented methyl butyrate (CH3H7COOCH3); orange-scented n-octyl acetate CH3COOC8H17); apple-scented isoamyl isovalerate (C4H9COOC5H11), etc., all have the above two characteristics. According to the stereochemical theory mentioned earlier, we know that the odor of a substance depends not only on the chemical composition of these substances, but also on their stereostructure. In addition, the concentration of an odor also affects the odor. For example, skatole in concentrated form is a nauseating stench, but when extremely dilute it becomes a pleasant odor.
A prominent feature of the olfactory system is that its sensory cells connect directly to the brain; in fact, it can be regarded as a special type of nerve cell. Other sensory systems, including taste, must pass through intermediate media before reaching the central nervous system. Another interesting fact is that the cerebral cortex can provide higher-level thinking ability and memory, while the pituitary gland can be regarded as evolved from the olfactory organ of the primitive brain. Therefore, odor can actually sometimes also evoke certain memories.
In land animals, the difference between taste and smell is very great. Odor diffuses in the air, while taste exists in solution. For aquatic animals the difference is not great, because chemical stimuli are all dissolved in solution.
Applications of Smell
Humans began producing various products to stimulate the sense of smell long ago. Although organisms evolved to the advanced stage of humans and acquired language, so that thought no longer needs to be transmitted through smell, several thousand years ago in ancient China the incense people burned and the perfumes sprinkled on clothes were probably the fragrant substances earliest produced by humans to stimulate smell. Perfumes were also widely used in Greece and ancient Rome. The sages in the Bible often carried gold, frankincense (blue storax), and myrrh; the latter two are gums used as perfumes. Only when the Crusaders brought perfumes back to Europe from the Arab world did Europe first learn to make perfume.
With the development of production, people's demand for perfumes has grown exponentially. After synthetic perfumes were put into production at the end of the 19th century, the output and variety of perfumes continued to increase. Initially perfumes were processed from flowers or other parts of plants to obtain essential oils. Processing methods could use steam distillation or extraction with volatile solvents such as benzene and ether and oils and fats; or extraction by pressing. Because essential oils are present in plants in very small amounts, the yield is very low. About 1 kg of rose oil can be produced from each ton of roses. The main components of essential oils are terpenes. Turpentine contains large amounts of terpenes, so turpentine is a major raw material for perfume production. For example, geraniol in it has a rose fragrance. Some perfumes are also obtained from the secretory glands of certain animals, such as castoreum from the Canadian beaver, civetone from the American civet, and musk ketone from the musk deer. Ambergris is a waxy high-grade perfume secreted by whales (sperm whales). Perfume is usually made by mixing essential oils, animal perfumes, and chemical additives in alcohol. It should be pointed out that the mixed perfume must have stable chemical properties, but it must not be too stable. Moreover, for ordinary people, the odor and the pH to the skin must both be moderate. Highly skilled experts with keen smell can blend various perfumes into intoxicating, high-quality essences. When blending perfumes, these experts rely entirely on their many years of practical experience and extraordinary sense of smell. Therefore, people with dull smell cannot undertake this work.
Besides perfume, a large number of commodities are also treated with perfumes to give them pleasant odors, such as shaving cream and cosmetics. Diapers, toilet paper, and scented paper handkerchiefs, on the other hand, are treated with a less obvious fragrance. Even in dishwashing water, hand soap, household cleaners, and detergents, people often add the fragrance of pine or lemon.
There are also some unpleasant odors in nature. The foul smell of rotting meat and the odor emitted by excrement are mainly due to compounds such as putrescine (H2N-(CH2)4-NH21,4-diaminobutane), cadaverine (H2N-(CH2)5-NH21,5-diaminopentane), and skatole. These substances are products of the decomposition of amino acids that make up proteins. These extraordinarily foul odors are also useful. They can help us identify spoiled food, and these gases can also be added to odorless natural gas so that we can conveniently detect leaks in natural gas pipelines.
In daily life we always dislike those unpleasant odors. So how can we resist these odors and prevent them from stimulating our olfactory organs? One method is to remove the molecules of foul odors by surface adsorbents or chemical reactions; another method is to cover up unpleasant odors with stronger fragrances; the third method is to weaken or anesthetize the olfactory nerve endings. At this time, although the odor still exists, it no longer causes a reaction in the olfactory nerves. In recent years, the most important research and application of smell is probably the study of insect sex pheromones. As mentioned earlier, the lives of insects depend on their keen sense of smell; even a very tiny amount of sex pheromone can
act on insects. The amount of sex pheromone contained in an insect's body is very, very small, so separating them and clarifying their structure and characteristics is an extremely difficult task. But considering the huge economic losses caused by insect damage to crops and other agricultural products, and the economic benefits that may be brought to humankind by artificially controlling the behavior of some beneficial insects, scientists have overcome all kinds of difficulties to engage in research on sex pheromones. In 1959, humans isolated and identified an insect sex pheromone for the first time: the silkworm moth sex attractant. This work was obtained by a group of German workers who spent several years cutting the abdominal tips of more than 500,000 unmated female moths. The pure sex pheromone product obtained this time was less than one hundredth of a gram, named bombykol [H3C-CH2-CH2-CH=CH-(CH2)8-CH2OH]. Some sex attractants, such as the sex attractant of the gypsy moth, have been artificially synthesized and widely used as a new type of insecticide. These attractants need only be applied in extremely small amounts to lure large numbers of male moths from several thousand meters away and then kill them with drugs. A higher concentration of attractant can also be released to confuse male moths and prevent them from mating, making these pests extinct. Because this insecticide uses very little dosage, is very economical, and does not cause environmental pollution, it has attracted increasing widespread attention.
Through in-depth research on these pheromones, it was found that insects use pheromones with very high specificity. So-called specificity is what we often call "one key opens one lock": each pheromone acts only on a certain behavior of a certain insect, and only in this way can confusion be reduced in nature. Bombykol is released by female moths to attract male moths; heptanone is released by ants to alert their companions. People have studied using it to repel mosquitoes and ants from disturbing humans and livestock. The pheromone molecules insects use for alarm are generally relatively small, so that they can volatilize quickly, take effect rapidly, and do not require high species specificity. Therefore, some drugs that repel mosquitoes and flies can also drive away ants.
Now we have only taken the first step in the study of smell, or rather we have only grasped a few words of the "language of the nose," so we still cannot precisely understand the meaning expressed by this language. With the development of science and technology and our unremitting efforts, one day the mystery of smell will be completely uncovered.
Soap and Synthetic Detergents
In order to be neat and attractive, people must frequently wash clothes, bedding, and daily-use tableware and tea sets. Therefore, soap and various detergents have become inextricably bound up with our lives.
The invention of soap came much earlier than that of detergents. It is said that as early as more than 3,000 years ago, on Mount Sapo outside the city of Rome, it was accidentally made by people. On this sacred mountain, when people burned offerings, fats and oils dripped onto the plant ash and became the most primitive soap, and this soap seeped into the surrounding clay. People found that when they sat on this clay, clothes stained with the clay actually became easier to wash clean than before. People began to revere it as sacred soil, and only later did they realize that this was an accidental harvest of human labor.
In 70 AD, the Roman scholar Pliny described the process of making soap from goat fat and wood ash. In this process another substance had to be added - sea salt. It could make the soap float on top of the mixture, which is what we today call salting out. This record is probably the earliest description of the soap industry. Because production was very low at the time, it could only be used by wealthy people, and was a luxury for the filthy. In 1791 the French chemist Nicolas Leblanc used an aqueous sodium chloride solution by electrolysis to produce sodium hydroxide, and the reaction equation is:
2NaCl + 2H O ?electro??lysis? 2NaOH + H ↑(gas) + Cl ↑(gas),
From then on, soap became something that ordinary people could all use. However, not everyone knew what soap actually was. From 1811 to 1823, after M.E. Chevrenl studied soap products, he satisfactorily explained what soap is and the chemical reaction for making soap. As scientists clarified the principle of soap's stain removal, various synthetic detergents also emerged accordingly.
Chemical Properties
Soap is actually the sodium, potassium, or triethanolamine [N(CH2CH2OH)3] salt of a long-chain organic carboxylic acid. These salts of other carboxylic acids are also industrial soaps, but they have no stain-removing or cleaning effect. Because the triethanolamine salt can dissolve in organic solvents, it can be used as a dry-cleaning agent. The equation for making soap is:
The above reaction can explain the process by which the ancient Romans made soap. The animal fat used as sacrificial offerings contained triglycerides, and the hydrolysate of wood ash contained potassium hydroxide or sodium hydroxide. When they were heated together, the fat was decomposed to produce a small amount of glycerol and soap.
If some salt is added to the viscous mixture for making soap, the soap floats on the liquid surface. This process is called salting out in industry. Then it can be scraped off. The soap obtained in this way contains 50%-60% water and is
pasty. If it is continuously heated to remove water, when about 30% water remains it can be made into a solid, cake-like bar, and after it is air-dried until only 10%-15% water remains, it can be cut into pieces. If further dried until it contains
only 5%-10% water, it can be made into powder.
Soap made from natural raw materials uses 4 kinds of fats: beef tallow, palm oil, coconut oil, and olive oil. For an organic acid to have washing ability, it must contain a long chain of more than 9 carbons, and the washing ability increases
as the carbon chain grows. However, soaps whose molecules contain more than 18 carbons are insoluble in water, even in hot water. Oleic acid (which contains exactly 18 carbons) is a very good detergent because its cis double bond is between the ninth and tenth carbon atoms, that is, right in the middle of the molecule.
Therefore, soap containing 18 carbons has relatively good washing ability, while soap whose molecules contain 12 carbons has enhanced solubility in water. Soaps composed of long-chain molecules containing more than 18 carbons are only used as scouring fillers. This kind of scouring agent needs stain-removing ability and does not need solubility.
Ever since people understood the principle of soap's stain removal, they have tried to improve its performance. Because soap has quite a few drawbacks. For example, it does not dissolve well in cold water and only dissolves better in hot water; in acidic solution it cannot properly perform its washing function, because in acidic solution it decomposes into insoluble acidic soap and lumps of fatty acid. In addition, soap reacts with elements in water such as calcium, magnesium, aluminum, and iron (forming so-called metallic soaps). This is the reason why basins and buckets show ring-shaped dirt after holding soapy water, and why fabrics show a faint film after being washed with soap. Soap is a very good cleaning agent in soft water. But unfortunately, the water we use in daily life, especially the water used in vast rural areas, is often hard water.
To improve soap's washing performance, chemists first had to clarify the principle by which soap removes stains. The process of stain removal is to remove dirt and grease with a very thin film - this film carries the dirt into solution, where it is emulsified or suspended and removed. In addition, as a detergent it must be able to reduce the surface tension at the water interface, so that the washing liquid can penetrate into the tiny gaps in fabrics, thereby speeding up the process of fabric wetting.
In fact, most organic detergents are made into polar molecules, with the molecule consisting of a long chain of 12-18 carbon atoms. One end contains a hydrophobic group (water-repelling), and the other end is a hydrophilic group (water-attracting). So how do soap and detergents remove stains?
Principle of Stain Removal
For a substance to have stain-removing ability, it must first be able to reduce the surface tension of the solution. The surface tension of pure water is 272 dynes per centimeter. But as an effective detergent it must reduce the surface tension to 230 dynes per centimeter, and only a very small amount of detergent is enough to reduce the surface tension to this value.
The typical force acting on a water molecule can make molecules on the water surface enter the solution—
—this produces surface tension. When soap molecules are added to water, they float to the surface, because the organic end (hydrophobic) is repelled by polar water molecules. Because soap molecules at the water surface are repelled by water molecules, a force is produced that opposes the mutual attraction of water molecules, and as a result the surface tension is reduced. When soapy water is added to fabric fibers, the oil attached to the fabric surface gathers into small oil droplets and leaves the fabric surface. The organic end of the soap dissolves in the oil and makes it leave the fabric fibers. At the same
time, the water keeps churning below, speeding up the rate at which the oil droplets leave. The polar groups in cotton fibers (such as the hydroxyl group -OH in cellulose) can attract water, causing the water to diffuse (penetrate) throughout the fabric. Overall, the reactions for removing dirt and stains are broadly similar. However, because dirt may be electrically neutral,
or positively charged, or negatively charged. Therefore, some modifications to this simple theory are also necessary.
Synthetic Detergents
Although soap is a fairly good detergent, chemists still wanted to improve it. The earliest attempt was made in 1860, when scientists sulfonated castor oil into sulfonated castor oil (Turkey red oil). Because Germany lacked fats and oils during World War I, scientists were prompted to research new detergents.
Fritz Gunter invented 1,4-diisopropylnaphthalene-6-sulfonic acid and sodium dibutylnaphthalenesulfonate. Although they were not very ideal detergents, they were enough to meet the German industrial demand for detergents at the time.
In 1933, Procter and Gamble produced the first household synthetic detergent. This synthetic detergent penetrated into soiled fabrics over a larger area than soap, and did not leave a film that interfered with dyeing. Moreover, it could also dissolve in cold water, and hard solutions and hard water had no effect on it.
From then on, with the development of the synthetic fiber industry and the increasingly strong call for women's liberation from housework, the synthetic detergent industry emerged and developed rapidly. Now, household detergents usually include some or all of the following ingredients: synthetic detergents; builders that remove calcium and magnesium ions; emulsifiers; bleaching agents; anti-corrosion agents; anti-caking agents; softeners; dyes; fragrances; and some also contain a small amount of enzymes.
Synthetic Detergents The molecular structure of synthetic detergents is similar to that of soap, and both contain hydrophilic groups and hydrophobic groups. The hydrophilic end can be cationic, anionic, or nonionic.
Because most fabrics acquire a negative charge during washing, the vast majority of detergents on the market are anionic detergents. Cationic detergents are used in industry, for example, for cleaning beverage bottles and various vessels used in brewing. Nonionic detergents are mostly used in washing machines, because when washing clothes in a washing machine one always hopes for less foam, and too much foam affects the rotation of the pulsator and reduces cleaning ability. Adding 2-octanol silicone or 2-ethylhexane silicone to anionic detergents can also achieve the purpose of reducing foam.
Builders (Synergists) They are used to complex the ions that cause water hardness (mainly calcium and magnesium ions, as well as iron, aluminum, and other ions), causing them to enter the solution, thereby keeping dirt suspended in the solution and preventing it from settling out. At the same time, builders can give the washing water appropriate alkalinity, thereby helping to dissolve acidic dirt. The most commonly used builders are phosphates, but carbonates, silicates, or
borates are sometimes also used. The best builders are sodium tripolyphosphate (Na5P3O10) and sodium pyrophosphate (Na4P2O7).
Sodium carbonate (Na2CO3) cannot complex calcium and magnesium into solution; instead, it forms granular carbonate precipitates,
which deposit at the bottom of the washing machine. This point has already been discussed in high school chemistry classes.
Emulsifiers Their role is to prevent dirt particles from redepositing on fabrics, keeping the dirt suspended in water so it can be rinsed away. The most common emulsifier is carboxymethyl cellulose, whose structure is: cellulose-OCH2COO-Na+, which can give dirt particles a negative charge, thereby making the dirt repel one another, and also making them repel the usually
negatively charged fabric fibers. Therefore, they neither aggregate to form precipitates nor easily adhere to fabrics.
Bleaching Agents When the pigments in clothes are exposed to sunlight, oxygen, and air pollutants, their chemical structure changes, causing the clothes to fade or darken. But the calcium salt of hypochlorous acid [Ca(ClO)
2], or the sodium salt [NaOClO], can produce chlorine gas in water, and chlorine gas can keep the pigments at their original color.
Therefore, these hypochlorites are often used as bleaching agents. Anti-Corrosion Agents Sodium silicate (Na2Si3O7) is a waterproofing agent; it can form a layer on metal surfaces that is
impermeable to water, thereby protecting this part of the metal from corrosion. If it is added to detergents, it can prevent metal parts such as washing machines, metal buttons, and zippers from corroding. Sodium silicate not only has an anti-corrosion effect, but is also a kind of builder. Of course, it also protects our resources. Because of it, the service life of washing machines is extended, and we do not need to produce more new washing machines.
Anti-Caking Agents If detergents become damp and cake during storage, the amount of detergent used will increase when they are used. This is not only because caked detergent is not easy to dissolve completely, but also because it easily deposits on fabrics. This both wastes detergent and shortens the life of fabrics. Usually, adding a small amount of
sodium sulfate (Na2SO4) can effectively prevent caking.
Softeners Most softeners are cationic substances. When fabrics are washed, the fibers often acquire a negative charge. In this way, after cationic reagents are added, they tend to combine with the fabric fibers. Softeners also have a long organic chain-like "tail," which acts like a lubricant and gives people a soft hand feel. Softeners also have an emulsifying effect and can retain moisture, thereby reducing the accumulation of static charge on the fabric surface. Therefore, the hand feel performance is improved.
Colorants and Fragrances If soap and detergents were all made white, consumers would inevitably find it very dull. If we add a small amount of pigment to make these detergents appear light blue or pink, consumers will feel more comfortable. In addition, soap and detergents undergo slow chemical reactions during storage, producing unpleasant odors. To counteract these odors, some fragrances must be added. Enzymes A few years ago, enzyme-containing detergents began to appear on the domestic market. When using this kind of detergent, we often have to soak the clothes in warm water for a while. Because enzymes are inactive in hot water. Enzymes are protein-type chemical reaction catalysts; they can break down large molecules such as proteins and carbohydrates, thereby speeding up the washing speed of the detergent. Clothes with a lot of juice stains are especially suitable for enzyme-containing detergents. Usually used
enzymes are proteases for degrading proteins and amylases for decomposing starch. For a period of time, because these enzymes caused severe skin allergies in some people, enzyme-containing
detergents once disappeared from the market. Now, because these shortcomings have been overcome and because of their good washing ability, they have returned to the market and are deeply welcomed by consumers.
Foaming Agents Foam can make suspended oil or dirt float on the water surface and be rinsed away. Generally speaking, reducing surface tension increases foam, and nonionic detergents are not very ideal for foaming. There is a class of nonionic compounds that do not foam; they produce foam for only a very short time. When a solution containing this kind of detergent
flows into ditches, the foam disappears. Some foaming agents are added only to satisfy consumers' psychology. Because consumers always think that if the washing water has no foam, it has no washing ability. This view is correct for soap, but not necessarily so for synthetic detergents.
Detergents People have found that when glassware is washed in a washing liquid, the stains on it are rinsed clean. These stains are caused by a small amount of insoluble salts in the rinse water. If the detergent contains sodium chlorophosphate produced by the reaction of chlorine gas with trisodium phosphate, it can dissolve those insoluble salts, thereby making the glassware clean and sparkling.
Environmental Pollution Problems
In recent years, the use of soap and synthetic detergents has increased day by day. In the United States, the average annual consumption of soap and detergents per person is as much as 28 pounds. In our country in recent years, in addition to daily washing powder, various new detergents such as dishwashing liquid, shampoo paste, and perfumed bath lotion have continuously poured onto the market. This has created a new problem
—the problem of environmental pollution. The earliest anionic synthetic detergents used, especially sodium alkylbenzenesulfonate (ABS), have this pollution
problem. Because the hydrocarbon group in its molecule is branched, it is very difficult for bacteria to decompose (also called degrade). Therefore, the concentration of this detergent in the sewage of sewage treatment plants is often very high.
In 1965 the U.S. government announced that synthetic detergents produced must be biodegradable. Straight-chain hydrocarbons are easily decomposed by bacteria into short chains containing only two carbons, while branched hydrocarbons are not easily decomposed by bacteria into short chains containing only two carbons; branched hydrocarbons are not easily decomposed by bacteria. At present, linear alkylbenzene sulfonate (LAS) is commonly used. LAS detergents are cheaper than ABS and can be made from petroleum by-products.
Because anionic synthetic detergents can kill bacteria, they have been widely used, but their sewage treatment has become a headache. Detergents in sewage are often degraded by bacteria in activated sludge. When the concentration of anionic detergent is 150 to 200 ppm, there is a fatal danger. Fortunately, in general wastewater treatment plants its concentration is rarely higher than a few ppm; this concentration can kill those unpleasant intestinal bacteria and can also reduce sludge residues in sewers, thereby cleaning the pipes and keeping water flowing unobstructed.
In addition, the builders contained in detergents, sodium tripolyphosphate and sodium pyrophosphate, are very good chemical fertilizers and can promote the growth of aquatic plants such as algae. This is called the "eutrophication" of water quality. However, when things reach an extreme, they reverse; the crazy growth of aquatic plants can block river channels and lake branches, seriously affecting water transportation. In addition, when large numbers of aquatic plants die, they consume oxygen in the water and also release toxic gases such as methane and hydrogen sulfide that poison the water quality, making it impossible for fish and other aquatic animals to survive. According to statistics from Britain, the United States, and other countries, 30%-70% of the phosphorus in urban sewage comes from detergents. The result of "eutrophication" turns vibrant waters into "dead lakes" and "sewers."
In short, with the improvement of people's living standards, various new detergents are constantly being put on the market. These products enrich our lives and bring us a neat, clean, and comfortable environment. But at the same time, we must pay sufficient attention to the water quality pollution caused by washing water and prevent trouble before it happens.
Dangerous Chemical Substances
Lead Pollution and Its Prevention
The ancient Roman Empire once dominated for a time. However, more than 100 years after its heyday, the ancient Roman Empire went from bad to worse and rapidly moved toward destruction under the situation of foreign invasion and internal chaos. In recent years, research on why the once illustrious ancient Roman Empire quickly declined has gone beyond the scope of pure history.
Some scholars found that the remains of ancient Romans contained large amounts of lead, and from this concluded that the ancient Roman Empire was a victim of lead pollution. Because the ancient Roman aristocracy habitually used lead vessels (bottles, cups, pots, etc.) and cosmetics containing lead compounds, this led to death from chronic poisoning.
The common people of ancient Rome were not necessarily unconnected to lead either. Although they could not enjoy high-grade lead vessels and did not need cosmetics, please do not forget that ancient Rome once had the most advanced water supply and drainage system of ancient humanity, and the water pipes used to transport drinking water at that time were made of lead. On the one hand, lead ions would directly enter the human body; on the other hand, the drinking water of the ancient Romans was rich in carbon dioxide, which reacted with lead to form water-soluble lead hydrogen carbonate, and then entered the human body and underwent a replacement reaction with calcium in the bones, thereby causing chronic disease.
Lead not only led to the destruction of the ancient Roman Empire, but also harms humans today. In the northeastern suburbs of Paris there is a large area densely packed with old residences built before 1948, and the vast majority of the residents in them are the urban poor and immigrants from North Africa and elsewhere. Among the children living in these old buildings, strange incidents of sudden convulsions, coma, and even unexplained death occur from time to time.
Not long ago, the French health department investigated 102 residences in the above areas. When they examined the blood of children in these residences, they found that about 30% of the children had blood lead concentrations as high as 150 micrograms per liter. According to standards, a blood lead concentration of 100 micrograms per liter is already severe lead poisoning!
Then where did the lead poison in these children's blood come from? It was found that the houses they lived in all had histories of more than 40 or 50 years, were in long disrepair, were damp, and the paint on the walls had long since loosened and peeled off. Sadly, these children often dug off paint fragments with their fingernails and put them in their mouths to chew, because this stuff had a sweet, greasy taste. How could they know that these paints all contained lead components, and it was precisely these lead compounds that produced a little sweetness.
Lead is severely toxic to humans, and even more so to children. Because lead has a very strong affinity for the nervous system, and children's nervous systems are in a period of development, they are more susceptible to damage, which often leads to lifelong ailments such as epilepsy, poor intellectual development, and muscle paralysis. In addition, because lead's metabolism in the body is similar to that of calcium, it can replace calcium and be stored in the bones. Children in the midst of growth and development originally need large amounts of calcium; when lead "fish in troubled waters" and enters the bones, it causes lead accumulation and becomes a hidden danger.
To prevent such tragedies from recurring, the fundamental thing is to eliminate lead components from paint, such as not using white lead or red lead to make white and red paints. At present, many countries in the world have already done this. For example, as early as 1981, Britain legislated to prohibit adding lead components when manufacturing paint.
However, at present the most widespread lead pollution harmful to people does not come from paint, but from gaso-
line.
The fuel in a gasoline engine must be compressed before ignition. The higher the degree of compression, the higher the engine's working efficiency. But people often cannot obtain very high working efficiency, because when the fuel is compressed to a certain degree, it will self-ignite before ignition. In view of this, people enlisted the help of a compound called tetraethyl lead: adding less than 1 gram of tetraethyl lead per liter of gasoline can prevent the fuel from detonating too early. Tetraethyl lead is toxic, so people add some pigment to gasoline blended with tetraethyl lead, making it rose-colored, green, orange, or other colors to distinguish it. But the problem is that the lead blended into gasoline itself
cannot burn, and can only drift into the atmosphere with the emission of automobile exhaust. In order to change the situation of leaded gasoline polluting the environment, people began looking for substitutes for tetraethyl lead
long ago, and have already achieved results. Japan began producing unleaded gasoline in the early 1970s, and by 1975 had achieved unleaded gasoline; the United States began producing unleaded gasoline in 1975, and by 1988 achieved unleaded gasoline. The U.S. Congress also legislated in November 1990: strictly prohibiting the use of leaded gasoline in the United States; the European Economic Community also promulgated regulations in 1991 for automobiles to use unleaded gasoline. By 1994, 99% of countries in the world had prohibited the use of leaded gasoline.
However, for various reasons, our country is still using leaded gasoline, but is already actively preparing for the use of unleaded gasoline: in 1991, China's petroleum department promulgated a national-level standard for "unleaded gasoline for vehicles"; in 1992, in Shuangyushu, Haidian District, Beijing, China's first unleaded gasoline station with a green sign appeared; subsequently, senior officials of China's Ministry of Transport let it be known to society that China strives to achieve unleaded gasoline by 1996??
Indoor Environmental Pollution
After his defeat at Waterloo, the outstanding hero of his generation Napoleon was imprisoned on the island of Saint Helena in the South Atlantic,
and died suddenly of acute illness in 1821. Some pathologists verified that he died of arsenic poisoning, because his attending physician recorded that "in the final stage of his life, Napoleon's hair fell out, his teeth were exposed to the gums, his face was ashen, his feet were swollen, and he died with his heart beating violently." These symptoms are completely similar to the symptoms of arsenic poisoning.
By the 1960s, an unexpected piece of news came: a lock of Napoleon's hair had been discovered! It turned out that when Napoleon died, his servants, in order to preserve his remains, used the method of plaster casting, that is, first shaving off the hair, applying plaster paste to the face to obtain a negative mold, and then turning it into a death mask. At that time, a personal guard, for permanent remembrance, devoutly preserved a lock of Napoleon's hair.
This news greatly excited some scientists interested in the cause of Napoleon's death: there was hope of solving this historical mystery! Because hair conceals the secrets of the entire human body. Each hair contains about more than 20,000 cells and contains multiple chemical elements. Because the concentration of the contained elements is high, the sensitivity and accuracy of testing exceed blood and urine tests. Therefore, in recent years, the simple and accurate "hair diagnostics" has developed very rapidly.
After British scientist Smith used neutron activation analysis technology to analyze several strands of Napoleon's hair, he determined that he died of arsenic poisoning, because the arsenic content in his hair was 13 times that of normal people. But where did the fatal arsenic
come from? After analysis, some historians concluded: from the wallpaper in Napoleon's room.
At that time, the walls of Napoleon's room on Saint Helena were pasted with green wallpaper. The green pigment at that time contained arsenic compounds. Under ordinary circumstances, this arsenic compound was relatively stable and would not harm people. But in the humid environment of Saint Helena, the wallpaper gradually became damp and moldy, and the mold converted these arsenic compounds into volatile substances that dispersed in the room. Year after year, it finally caused Napoleon's death from chronic arsenic poisoning.
The answer to the mystery was so cruel: pollution caused by interior decoration led to the death of an outstanding hero of his generation! However, perhaps even more shocking is that the harm modern humans suffer from indoor environmental pollution is absolutely no less than in Napoleon's time!
One day in July 1994, a 38-year-old female worker in Nanjing excitedly sent a pennant to the hematology department of Jiangsu Provincial Hospital of Traditional Chinese Medicine, thanking the doctors for giving her a second life. This female worker had moved into a newly decorated residence. The freshly painted furniture and the spray-coated wall surfaces made her feel the warmth of modern life. However, one month later she felt dizzy and weak, and then a large number of bleeding spots appeared all over her skin. Blood tests showed that hemoglobin, platelets, and white blood cells were all reduced, and she was diagnosed with "aplastic anemia." Seeking treatment in many places produced little effect, and later she actually had to rely on weekly blood transfusions to sustain her life. Fortunately, the doctors in the hematology department of the hospital of traditional Chinese medicine promptly found the cause and prescribed the right medicine, so that she recovered her health.
The doctors in that department believed that what made this female worker develop a blood disease was precisely those painted furniture and spray-coated walls that had once given her warmth. So-called spray coating is actually a novel colorful interior wall coating. In this respect, it is not very different from paint; both are made by adding solvents to polymer resin raw materials. Generally speaking, the resin raw materials used are not toxic in themselves; the problem is that some solvents and other additives are quite toxic. After being coated onto furniture and walls, the solvents and additives slowly volatilize and will harm people's health. For example, the solvent xylene in spray coating and the solvent benzene in paint are both toxic. If a person lives in a room that has not long been painted, they may suffer chronic poisoning.
Indoor environmental pollution also comes from some other factors. Modern furniture is mostly made from artificial board materials such as plywood, fiberboard, and particleboard, and they release relatively strong formaldehyde odor in the room. Formaldehyde is a colorless irritating gas. When the concentration is high, it can cause nausea and vomiting, asthma, and emphysema, and can also induce skin cancer. Chemical fiber carpets, floor leather, plastic veneer panels, and other materials also release the strange odor of formaldehyde. It is generally believed that in modern decorated residences filled with new-style furniture, formaldehyde is the most widespread pollutant in the home.
Now, in order to eliminate pests such as mosquitoes, flies, bedbugs, and cockroaches, many families keep insecticides. Recently, spray insecticides have been used more, mostly in cans with nozzles. When using them, one only needs to gently press the nozzle to spray out an aerosol, which is very convenient. The chemical structure of this type of insecticide is similar to pyrethrin, and they are called pyrethroid insecticides, such as deltamethrin (namely Decis), fenvalerate (namely Sumicidin), cypermethrin, and so on, all belonging to this class. This type of insecticide is highly toxic to insects but less toxic to humans, yet it is not absolutely non-toxic. This type of insecticide is mostly difficult to dissolve in water and easily soluble in organic solvents such as acetone and toluene, and these also often have a certain toxicity. The low-boiling aerosol propellants loaded in the cans, such as Freon, also have toxicity that cannot be ignored.
In a survey report in the late 1980s, American scientists revealed that indoor toxic substance pollution is more serious than outdoor pollution, sometimes even as much as 100 times. In a survey conducted in 1994 by the relevant departments of our country, it was also found that the pollution level of indoor air in Chinese cities is 56 times more serious than outdoors.
The Harm of Radon Gas
"Leukemia!" Facing the same diagnosis for 4 university students, the department head of a certain university was stunned. What shocked him even more was that the 4 students actually lived in the same dormitory! The department head felt that this matter was somewhat strange, so he invited some medical chemistry experts to inspect the dormitory.
The dormitory manager was called over, and upon asking, it was learned that this dormitory building had actually been in use for many years. This dormitory was on the ground floor, right next to the toilet. Because the sewer of the toilet had leaked for a long time, the cement floor of the dormitory and the wall next to the toilet were covered with stains and smelled unbearably foul. For this reason, during the summer vacation a year and a half earlier, the school had carried out major repairs on this dormitory and the toilet, repaired the sewer, rebuilt the partition wall between the dormitory and the toilet, and relaid the cement floor.
"It seems the problem lies here." The experts had a slight realization, because these students had precisely enrolled a year and a half earlier, and upon enrolling had moved into this just-repaired dormitory. The experts chiseled off some bricks and cement to take back for testing, and finally the truth came out: these building materials used in the repairs contained radioactive substances, which would release radon gas and cause malignant lesions in the human body. The university students became ill precisely because they were murdered by this invisible "killer," radon.
Experts were not unfamiliar with radon; it was precisely in people's research on radioactive substances that it was discovered. It can be said that from the day of its discovery, people have been wary of radon.
In early 1899, British scientist Rutherford and his collaborator Owens were studying the radioactivity of thorium compounds. Once, Owens accidentally opened the laboratory door, and just then a gust of wind blew through. The experimenters noticed that the radiation intensity of the thorium products suddenly decreased. At first, they ignored this matter. But later, many similar situations made them notice that even a slight air flow would cause most of thorium's radioactivity to disappear. Based on this, Rutherford and Owens determined that thorium continuously releases a gaseous radioactive substance, which they called thorium emanation.
In 1900, when the Curies were studying radium compounds, they also discovered that after radium compounds were placed in the air, the air itself also became radioactive. In the same year, Germany's Dorn and Debierne also discovered from radium that a radioactive gas was released. They called it radium emanation. In 1903, Debierne also discovered actinium emanation from actinium.
In 1908, British scientist Ramsay determined that these emanations themselves were a new element, and like some inert gases already discovered, were an inert gas. Thus, a new member was added to the periodic table - element No. 88, radon.
Radon is a product of the decay of radioactive elements such as uranium and radium, and its discovery was a major event in the history of science. Because this was not only the discovery of a new element, but also the discovery that in nature one element can transform into another element. This provided scientists with a reliable basis for using artificial methods to turn one element into another.
Although the discovery of radon was of great significance, it is harmful to human health. Because radon can decay into polonium, and then polonium decays into bismuth and lead particles. When people inhale excessive radon gas, the lead and bismuth particles produced during radon decay accumulate on the walls of human bronchi and pulmonary trachea, damaging human cells and inducing cancerous changes in cells. In more developed countries, radon gas is the factor causing lung cancer second only to smoking. Environmental incidents caused by radon have also been disclosed in our country. In Lujiabang, a mountain village on Hangzhou Bay,
the nearly 60-year-old Old Zhao built a new house with two rooms upstairs and two downstairs. But not many days after moving in, first his mother in her 80s was taken by lung cancer, then his wife, who had always been in robust health, became bedridden, and finally Old Zhao also fell ill. Some superstitious people believed this was a "haunted house," but Old Zhao's burning incense and worshiping Buddha was of no help. Later, a survey team borrowed Old Zhao's house to store instruments and unexpectedly discovered that the radon content of this house seriously exceeded the standard. Only then was the mystery of the "haunted house" uncovered.
Some people believe that our country's current level of science popularization is relatively low, and if one investigates carefully, perhaps many inexplicable deaths and disease incidents can find their answers in radon.
It should also be explained that what can produce radon is not only some building materials. Rocks containing radioactive elements in the earth's crust always continuously diffuse outward a portion of the radon gas formed within them, so groundwater always contains more or less some radon gas. Before strong earthquakes, crustal stress activity strengthens, radon gas migration increases, and the content will also undergo abnormal changes. If the underground aquifer deforms under the action of stress, it will accelerate the movement of groundwater, enhance the diffusion of radon gas, and cause an increase in radon gas content. Therefore, measuring changes in radon gas content in groundwater is an important method of earthquake monitoring.
There are also other pathways for radon gas to enter indoors. After radon is produced in rock, a portion of it rises toward the surface through cracks in the rock layer and seeps into the soil. It can enter indoors from the foundation isolation layer or floor gaps of a house, and can also enter indoors through underground pipes. Because there is not enough time for dilution and decay, radon gas accumulates indoors, and when the concentration increases it becomes a "killer." Former U.S. Environmental Protection Agency administrator Thomas said that several million American households have radon gas concentrations at the edge of harm. And of the radioactive pollution humans currently receive, about
54% comes from radon.
The Anti-Poison Guardian "Activated Carbon"
In the former residence of the Russian scientist Zelinsky, there is a gas mask. What is surprising is that a gold medal hangs on this gas mask. Its origin must be traced back to World War I.
In the spring of 1915, on the western European battlefield of World War I, just as the German army and the Anglo-French allied forces were fighting a great battle in the Ypres region of Belgium, the German army, in order to break the deadlock on the battlefield, suddenly on
April 22 released No. 180 poison gas - chlorine gas - toward the positions of the Anglo-French allied forces. The thick, irritating yellow-green gas caused 5,000 deaths and 15,000 poisonings among the Anglo-French allied forces.
In battlefield investigations, scientists found that when the poison gas attacked, there was also a pig at the scene. At first, the poison gas choked it unbearably, so it desperately rooted in the soil with its mouth, and then buried its big mouth in the soft soil. Unexpectedly, this pig actually became a survivor of this poison gas battle! This matter aroused great interest among scientists. Through preliminary research, it was found that when the pig buried its mouth in the soil,
the soil particles blocked and adsorbed the poison gas in the air. That is to say, the soft soil played a role in filtering the poison gas, and the air the pig inhaled into its body was non-toxic gas. Therefore, scientists designed the most primitive gas mask - a mask filled with small soil particles. Later, based on the principle that sodium carbonate and sodium thiosulfate can react with chlorine gas:
Na2S2O3+4Cl2+5H2O Na2SO4+H2SO4+8HCl
a cotton cloth gas-protection mask soaked in solutions of these two substances was developed. But the effect was not ideal. First, the cotton mask did not have much adsorptive capacity; second, at best it could only defend against chlorine gas and could not deal with other toxic gases.
The person Russia sent to the front was the famous chemist Professor Zelinsky. After careful analysis, Zelinsky believed: cotton and soil have the ability to absorb gases because molecules exposed on the solid surface are attracted only by the molecules in the inner layer and on the left and right sides, and the attractive force is not completely canceled out; there is still residual attractive force that can attract gas molecules that come near it. The residual attractive force existing on the solid surface can exert an adsorptive effect on any gas. The larger the molecular weight of the gas, the greater the attraction of the solid surface molecules to it, that is, the easier it is to adsorb. Because the molecular weights of various poison gases are all relatively large. Therefore, cotton and soil have considerable adsorptive effects on various poison gases.
Thus, Zelinsky concluded: there is absolutely no need to find defensive products for each kind of poison gas, because the molecules on the solid surface have an adsorptive effect on any kind of poison gas. One only needs to choose a substance with a larger solid surface than cotton or soil, that is, with a greater ability to adsorb gases, and it can cope with all poison gases.
After experiments, Zelinsky chose ordinary charcoal as the adsorbent. As early as 1785, someone had discovered the wonderful effect of charcoal in adsorbing gases, but no one had used charcoal's special strengths to play a role. Zelinsky's experiments proved that charcoal itself can not only adsorb gases, but because of its porous structure, it can also let fresh air pass through unobstructed.
In order to strengthen charcoal's ability to adsorb chemical substances, Zelinsky, through continuous research, finally in
1917 obtained a special substance - "activated carbon." "Activated carbon" is a strong anti-poison guardian; it can intercept toxic gases and only let oxygen and
Other harmless gases pass through. Activated carbon is made by the dry distillation of wood, hard nut shells (such as walnut shells) or animal bones. Dry distillation means heating under conditions where air is excluded. Through dry distillation, the cellulose and lignin in the wood are all turned into carbon; at the same time, moisture and many volatile substances continuously escape, leaving countless pores in the carbon. The carbon made by dry distillation must then be treated with high-temperature steam at 800-900°C to clear out these blockages. Activated carbon made in this way is light, loose and porous. Every gram has a surface area of several hundred square meters, so its ability to adsorb gases is especially strong and its protective effect is even better.
.
With the help of a Russian engineer, Zelinsky also successfully designed a gas mask. This consisted of a short, thick canister fixed in front of a face mask, positioned right over the nose. The canister contained "activated carbon." When the attacking poison gas passed through the activated carbon, the poison gas was filtered out. Fresh air was fully supplied.
After the gas mask was sent to the front line, it stood the test of practice and won recognition and praise. It saved the lives of tens of thousands of soldiers during the Second World War, so it is no wonder that people wanted to pin a military medal on the gas mask.
"Activated carbon" also shines brilliantly in daily life and in science and technology. When you have diarrhea or abdominal pain from eating too much or from catching a chill, doctors often give you medicinal charcoal (activated carbon). Medicinal charcoal can adsorb debris in the intestines, reduce the irritation of this debris on the intestinal mucosa, and thus relieve pain and stop diarrhea. In sugar factories, activated carbon also plays an important role. Here, however, it is a decolorizing agent. Dark red raw sugar containing about 96% sugar, after decolorization with activated carbon as well as vacuum concentration, crystallization and other processing, is made into dazzling white refined sugar containing more than 99.7% sucrose - high-grade white sugar. It is also worth mentioning that when a spaceship travels through outer space, it must have a separate ecological system, in which the air is recycled after adding an appropriate amount of oxygen. The gas exhaled by the astronauts must first have its carbon dioxide absorbed by chemical substances and be absorbed through activated carbon to remove odors and other substances, and only then can oxygen be added and the air be recycled. The chemical substance contained in the activated carbon is sodium peroxide, in which
the source of oxygen is realized through the following reaction:
2Na2O2+2CO2 2Na2CO3+O2↑
Common Chemical Knowledge in Daily Life
Food The color, aroma and taste of food
The color of food is mostly artificial coloring, with food coloring added during production. Some foods also owe their color to certain natural pigments they contain. For example, the green color of the stems and leaves of green vegetables and of unripe fruit is chlorophyll, the red color of tomatoes is tomato pigment, and the shells of shrimp and crabs contain crustacyanin, which can show red when heated.
The aroma of food comes from volatile substances such as alcohols, aldehydes, ketones and esters. Fish, meat and eggs are all rich in protein. Protein itself has no umami taste, but after cooking it is hydrolyzed into various amino acids, and amino acids have a delicious taste. Among the amino acids, glutamic acid has the most delicious taste. "Monosodium glutamate" is the sodium salt of glutamic acid. If sucrose is diluted with water to 200 times, its sweetness can no longer be detected, but if monosodium glutamate is diluted with water to 3000 times, its umami taste can still be tasted! Recently a strong monosodium glutamate made by mixing sodium glutamate with sodium inosinate has been developed, and its umami taste is 40 times that of monosodium glutamate. The bodies of shrimp, crabs, snails and clams contain a great deal of succinic acid, so they have a unique umami taste that people love. The aroma of cinnamon is due to the cinnamaldehyde it contains, while the aroma of distilled liquor comes from the fusel alcohols and esters produced during fermentation. The aroma of bananas is the volatile isoamyl acetate, and the aroma of citrus fruits comes from the nerol they contain. As for the aroma of cakes and candies, it is due to the addition of artificial fruit flavorings.
In our country, people are accustomed to dividing taste into the "five flavors" of sour, sweet, bitter, spicy and salty. Sourness is caused by hydrogen ions ionized from various organic acids, and the strength of sourness depends on the concentration of hydrogen ions.
Vinegar contains about 3%-5% acetic acid, pickled vegetables contain lactic acid, and the sour taste in fruits, drinks or candies comes from the citric acid, tartaric acid, malic acid and vitamin
C and other components that make them up. Sweetness is caused by carbohydrate substances such as sucrose, fructose, glucose, maltose and lactose. When making cakes,
pastries, popsicles and ice cream, an appropriate amount of saccharin is also often added to increase sweetness. The chemical name of saccharin is o-sulfobenzimide, and its sweetness is about 500 times that of white sugar, but it has no nutritional value and can only stimulate people's appetite.
Most substances containing alkaloids have a bitter taste, such as coptis and cocoa. Tea leaves contain 5% caffeine, and the stronger the tea, the more bitter its taste.
Chili peppers contain capsaicin, scallions and garlic contain allicin, ginger contains gingerol, the spiciness of mustard and radish comes from mustard oil, and pepper contains piperine.
Everyone knows that table salt is salty, and when a compound contains both a monovalent cation and the anion of a monovalent acid, it has a salty taste. For example, the chlorides, bromides and iodides of potassium and sodium. For kidney disease patients who cannot eat salt, sodium malate, which can also produce a salty taste, can be eaten as a substitute.
Besides these "five flavors," there is one more taste, namely astringency. Some fruits, such as persimmons and plums, have an astringent taste because they contain tannic acid.
In short, taste is the different sensation caused by the chemical-physical stimulation of substances contained in food acting on the gustatory nerves.
Food Pigments and Flavorings Food pigments are dyes used to color foods and beverages, and are generally organic compounds. There are two types of food pigments: one is natural pigments, which are extracted directly from animal and plant bodies.
For example, yellow carotene can be extracted from carrots. A purple-red pigment called amaranth red can be obtained from red amaranth. Red pigment is extracted from the body and secretions of cochineal insects. The other type is artificially synthesized pigments made by chemical methods, and most of these pigments are synthesized using coal tar as a raw material.
Generally speaking, natural pigments have more advantages than synthetic pigments. Many natural pigments have certain nutritional value and medical value. For example, turmeric is extracted from the roots and stems of the traditional Chinese medicine turmeric, and has the effects of invigorating the blood, dispersing stasis, soothing the liver and relieving depression. Carotene can be converted into vitamin A in the body. However, extracting natural pigments from animal and plant bodies is very difficult and the yield is not high. Moreover, natural pigments have poor stability, cannot withstand high temperatures, and fear encountering acids and alkalis, so their color easily changes and disappears. Synthetic pigments, on the other hand, overcome the above shortcomings: their properties are stable, they are convenient to use, and the cost is low. But most artificially synthesized pigments are aromatic compounds with very large molecules. After people eat them, they generally cannot be digested and they have no nutritional value; they only play a coloring role and give people a feeling of beauty.
Adding flavorings to food can give food a pleasing aroma and enhance people's appetite. According to their source, food flavorings can also be divided into two major categories: natural food flavorings and synthetic food flavorings. Natural
food flavorings are mainly extracted from natural fruits. Such as coffee, cocoa, almond, orange, pineapple, bayberry and so on. This kind of natural flavoring can be directly added to fruit juice, soda and canned goods, and its aroma is the same as natural fruit aroma, making it delightful.
However, because natural flavorings are limited by their source and quantity, they are already far from meeting demand. In order to adapt to various different uses and meet people's ever-growing various needs, modern food flavoring technology has developed to a higher and newer level. With the help of various precision instruments, people analyze and study the aromas of various foods, identify the aroma-producing substances in them, and determine their chemical structures, so that they can be completely imitated and synthesized artificially. However, the aromas of various foods are each different, and their components are also quite complex. For example, as many as 81 aroma components have been identified in apples. The flavor components in the aroma of watermelon also number more than 80. The aromas of foods such as chicken, meat and fish are even more complex. Therefore, artificially synthesizing various food flavorings is a very meticulous and complex task, and this flavor-blending technology is also a combination of art and science. Food flavor-blending technicians can blend many kinds of natural flavorings, synthetic flavorings, and appropriate blenders and auxiliary agents into various food flavorings with a great variety of names and realistic aromas.
Food pigments and food flavorings enter the human body along with food, so the issues of their hygiene and non-toxicity are very important.
The Consumption of "Monosodium Glutamate" The taste of "monosodium glutamate" is very delicious, and when cooking dishes or making soup, people all like to add a little monosodium glutamate. What is "monosodium glutamate" made from? What benefits does it have for the human body? How much is appropriate to consume? Is it toxic if eaten in excess?
"Monosodium glutamate" is also called "wei jing," and its chemical name is sodium glutamate. It is a white crystal, often
made from wheat gluten or soybeans as raw materials through chemical processing. Wheat gluten and soybeans are both foods rich in protein. People put them into dilute hydrochloric acid and boil them for several hours, causing the protein they contain to hydrolyze and become various amino acids. Then the solution is evaporated and concentrated under low pressure, calcium carbonate and an appropriate amount of lime are added to remove the excess hydrochloric acid, and then alcohol is added. At this point glutamic acid precipitates out in the form of a double salt of calcium glutamate and calcium chloride. The precipitate is separated, dissolved in water, sodium carbonate is added, and the mixture is evaporated and concentrated to obtain white sodium glutamate crystals
- monosodium glutamate. Sodium glutamate can hydrolyze into glutamic acid, and glutamic acid is one of the amino acids. It has a strong umami
taste. According to experiments, after monosodium glutamate is diluted with water 3000 times, it still has an umami taste. Glutamic acid is a main component of human protein, so monosodium glutamate has relatively high nutritional value. Adding a little monosodium glutamate when cooking dishes or making soup makes the soup and dishes more delicious, so it can increase people's appetite and induce the secretion of digestive juices, which is beneficial to the digestion and absorption of food. Therefore monosodium glutamate also has the function of supplementing nutrition.
Some people believe that eating too much monosodium glutamate will cause poisoning, but this has no scientific basis. The Food and Agriculture Organization of the United Nations, the World Health Organization and the Joint FAO/WHO Expert Committee on Food Additives have long confirmed that long-term consumption of monosodium glutamate will not cause poisoning. Human brain tissue can oxidize glutamic acid, so consuming monosodium glutamate is beneficial for improving and maintaining brain function and making one feel refreshed. It also has certain therapeutic effects on neurasthenia and on improving the intelligence of children with neurological defects. Monosodium glutamate can also be used as a medicine. In medical treatment, oral administration or intravenous drip is often used to treat patients with hepatic coma. This is because sodium glutamate combines with excess ammonia in the blood to form glutamine, which can rapidly improve the symptoms of patients with hepatic coma, lower the blood ammonia value, and quickly restore them to a conscious state.
However, when using monosodium glutamate, special attention should be paid to temperature and to cooking methods. When cooking dishes, do not add monosodium glutamate too early. If cooking heats it to above 120°C, sodium glutamate will undergo a chemical change and become sodium pyroglutamate, which not only reduces the umami taste but also has slight toxicity. Therefore, when cooking dishes or making soup, it should be added just before taking the food out of the pot, and it should not be put into dishes to which alkali or baking soda has been added, so as to avoid the sodium glutamate in monosodium glutamate turning into disodium glutamate and losing its umami taste.
As for the amount of monosodium glutamate used, under normal circumstances, each person should not consume more than 6 grams of monosodium glutamate per day; otherwise, symptoms such as headache, nausea and fever may occur. Excessive consumption of monosodium glutamate may also lead to hyperglycemia. In addition, monosodium glutamate is not the more the better or the more umami. When cooking dishes or making soup, adding an appropriate amount of monosodium glutamate is enough to enhance freshness. If too much monosodium glutamate is added, instead one will feel the tongue go numb and produce a strange taste that seems salty but not salty and seems astringent but not astringent.
The Knowledge of Eating Sugar
Sugar is a necessity of people's lives and also an indispensable nutrient for the human body to maintain normal life. Eating sugar can replenish the energy consumed by the human body. Sugar is extremely easy for the human body to absorb. According to analysis and testing, after eating sugar
for 3 minutes, the blood sugar content in the blood can be increased. Therefore edible sugar is a very good health food for patients, the elderly and children. Although sugar cannot be used to synthesize protein, it can play a role in sparing protein. When the sugar supply is sufficient and sugar metabolism is normal, it is beneficial to the synthesis of protein in tissues. Conversely, when sugar is deficient or sugar metabolism is abnormal, protein decomposition will increase, and a negative nitrogen balance will appear. Under such circumstances, it is not beneficial to the synthesis of protein in tissues.
Although white sugar has high nutritional value, the science of eating sugar cannot be ignored.
The best times to eat sugar. 1. Before bathing: bathing causes a great deal of sweating and consumes physical strength, requiring replenishment of
water and energy, and eating sugar can prevent collapse. 2. Before exercising: exercise also causes sweating and consumes physical strength, and sugar can provide heat more quickly than other foods. 3. When tired and hungry: sugar can be absorbed into the blood faster than other foods and quickly raise blood sugar. 4. When dizzy and nauseated: eating some sugar can raise blood sugar, stabilize mood and help restore normality. 5. When vomiting and having diarrhea: because of digestive dysfunction, dehydration and insufficient nutrition, eating some sugar or drinking a little salt-added sugar water is equivalent to oral rehydration.
Times when it is not suitable to eat sugar. 1. Before meals: eating sugar will reduce appetite. 2. Before going to bed: sugar left in the oral cavity is conducive to bacterial reproduction, forming acidic substances that corrode the enamel on the surface of the teeth and form dental caries. 3. After eating one's fill: eating sugar at this time will make people gain weight and promote diabetes. 4. For those with dental disease: eating sugar will induce toothache and worsen the condition.
Eating too much sugar is very harmful. After white sugar enters the human body, it becomes glucose and fructose. Glucose then becomes pyruvic acid. If too much white sugar is eaten, pyruvic acid will increase rapidly, making the blood acidic. But human blood must remain weakly alkaline for the body to be healthy. Therefore, the human body must use alkaline substances such as calcium in the body to neutralize the excess acid, which may lead to calcium deficiency in the human body. According to research, calcium intake is inversely proportional to cancer incidence: the less calcium, the greater the chance of cancer. Calcium deficiency in the elderly can cause osteoporosis and make bones brittle and easily broken; calcium deficiency in children makes them prone to rickets.
Eating too much sugar also has the following harmful effects:
(1) It is easily converted into fat and stored, making one become obese and increasing cholesterol, thereby easily causing cardiovascular diseases such as vascular sclerosis. Therefore pastries and candies should be used sparingly.
(2) Children who eat a large amount of sugar over a long period are prone to dental caries.
(3) If a pregnant woman eats too much sugar, it will take away calcium from the fetus's body, making the fetal skull soft, so that it cannot pass through the birth canal during delivery, and sometimes it can also cause intracranial hemorrhage or plant the root of disability due to cerebral palsy.
For people suffering from diabetes, coronary heart disease and obesity, sugar consumption should be controlled, because sugar can induce increases in cholesterol and triacylglycerol in the blood, promote the development of hyperlipidemia, and cause atherosclerosis. The Uses of Table Salt
The greatest use of table salt is for eating. Apart from this, table salt is an important industrial raw material and can be used to manufacture soda ash, caustic soda, hydrochloric acid, polyvinyl chloride plastics and so on. Electrolysis of molten sodium chloride can produce metallic sodium. In agriculture, salt solution is used to select seeds, so as to ensure a relatively high germination rate, strong growth and increased yield. In large cities, sanitation workers use the method of spraying salt water to melt accumulated snow on roads, so as to ensure the safety of vehicles and pedestrians. In hospitals, salt water can be used instead of disinfectants to clean wounds, because a concentrated salt solution can strongly absorb the water inside bacterial cells, disrupting their metabolism and killing them.
In daily life, table salt also has many uses. If you can use it cleverly, it will bring you a lot of convenience. For example, when washing clothes, add a little salt and the clothes will not fade easily. When dyeing clothes, add a little salt and the color will be bright and firm. When deep-frying food, add a little salt to the pan, especially when frying fish; sprinkling a little salt on the fish flesh can prevent hot oil from splattering outward. In summer, sprinkling table salt on fresh fish and fresh meat can prevent the fish and meat from spoiling. Drinking a cup of salt boiled water after getting up in the morning can cleanse the stomach and intestines and keep the bowels open. Rinsing the mouth frequently with salt water can maintain oral hygiene and prevent disease. Soaking melons and fruits in 15% salt water for 20 minutes can have a disinfecting and sterilizing effect. Adding a little table salt to vinegar and taking it after boiling can stop vomiting and diarrhea; if hot water has reddened the skin, rubbing on a little table salt can reduce the pain.
Table salt is a friend of people's lives. Washing hair with salt water can help avoid hair loss. For newly bought porcelain or glassware, first boil it in salt water and it will not break easily; put a knife in salt water and soak it for half an hour, and sharpening it will be both labor-saving and easier to make sharp; for an egg with a broken shell, cooking it in salt water can keep the egg white from flowing out; tea stains on tea utensils can be removed by wiping them with a cloth dipped in table salt; when growing flowers in a vase, add a little table salt to the water and the flowers can stay fresh longer; adding a little table salt to paste can prevent spoilage and increase the viscosity of the paste; wiping furniture with table salt can make furniture smooth, clean and bright. Table salt is extremely abundant in nature. The vast sea is the main place where table salt resides. If all the table salt in seawater were extracted and spread over the surface of the Earth, it could form a large "salt blanket" about 40 meters thick, covering the Earth. Now, the world produces about 100 million tons of sea salt each year. If production continues at this rate, table salt can supply humanity for 500 million years!
Table Salt and Health
Table salt is an important condiment in daily life. Among the five flavors of sour, sweet, bitter, spicy and salty, the salty taste is the most basic. If it is missing from rice, soup and dishes, they will be bland and tasteless. More importantly, the human body cannot maintain normal physiological function without table salt.
Human blood contains about 0.6%-0.9% table salt. Under such conditions, the heart can beat normally and the muscles can maintain stimulus responsiveness. When the human body loses a large amount of water, it will at the same time be accompanied by a large loss of table salt. Doctors often use the method of subcutaneous or intravenous infusion of physiological saline (0.9% sodium chloride aqueous solution) for treatment. In the process of human metabolism, table salt is often excreted with sweat. Workers engaged in high-temperature operations, or after intense physical labor and strenuous physical exercise, should pay attention to drinking some salt boiled water so that the salt content in the body can be replenished. A lack of table salt in the human body can cause dizziness, fatigue and general weakness, reducing study and work efficiency. Long-term salt deficiency makes one prone to heart disease and can also produce "low sodium syndrome." Then, is it better to eat more table salt? No. If the human body takes in too much table salt, it will affect the normal progress of metabolism and cause an imbalance in acid-base balance. Eating too much salt easily produces sodium retention, and long-term sodium retention can lead to kidney disease and hypertension. Modern medical research proves that persisting in a light diet all year round can make people live longer.
It is not good for the human body to lack table salt, because the sodium element needed by the human body is mainly obtained from table salt; too much table salt is also not good, because taking in too much table salt can lead to some diseases. Then, exactly how much table salt should a person take in each day? According to research confirmation, a healthy adult eating 2-6 grams of table salt per day is enough. Of course, people doing heavy physical labor and sweating a lot can appropriately increase it somewhat, but it should not be too much. Generally speaking, each person eating 5 grams of table salt per day is beneficial and harmless.
The Institute of Nutrition of the Academy of Medical Sciences of the former Soviet Union recently developed a low-sodium table salt formula. In this table salt formula, potassium and magnesium, which can maintain normal heart muscle function, are used to replace sodium. The formula is divided into two kinds: one is salt for general people to eat, in which 1/3 of the sodium is replaced by potassium and magnesium; the other is medical table salt, in which 6% of the sodium is replaced by potassium and magnesium. Both kinds of salt are used as edible salt.
Beverages The Science of Tea Drinking
Tea is a commonly used beverage in our lives. Our country is the hometown of the tea plant and also the first country in the world to drink tea.
Tea can be divided into four major categories: green tea, black tea, oolong tea and scented tea. Green tea is made by collecting fresh tea leaves and putting them through processes such as de-enzyming, rolling and drying. Because it has not
undergone fermentation, the chlorophyll has not been destroyed and still maintains its original color, so it is called green tea. Black tea is made from fresh tea through processing and refining processes such as withering, rolling, fermentation and drying. The tea leaves
turn red-black because the chlorophyll is oxidized under the action of oxidase, so it is called black tea. Oolong tea is a semi-fermented product, and its nature lies between black tea and green tea. The jasmine tea commonly drunk in ordinary life is made by scenting fragrant, rich jasmine flowers with green tea.
It has both a fragrant aroma and a refreshing tea taste.
According to modern scientific analysis: tea leaves contain more than 320 chemical components, among which the most important are tea polyphenols, accounting for about 20%-30% of dried tea leaves. Experiments prove that tea leaves have a certain inhibitory effect on Staphylococcus and Escherichia coli, so drinking tea has a sterilizing and anti-inflammatory effect, which is related to tea polyphenol substances. Tea leaves contain about 5% alkaloids, among which the main one is caffeine (tea essence), which has the effects of exciting the central nervous system, promoting metabolism and strengthening the function of the heart and kidneys. Therefore, when we are tired, drinking a cup of tea makes us feel refreshed. It can stimulate the bladder to urinate, so tea is a very good diuretic. Tea leaves contain aromatic compounds, which can dissolve fat and help digestion. Therefore, after a rich feast,
drinking a cup of clear tea can cut the greasiness.
Tea leaves also contain about 8% protein, 2%-3% minerals, some sugar and various vitamins. Such as vitamin C, vitamin B1, vitamin B2, vitamin P and so on. These vitamins are all nutrients needed by the human body, and have preventive effects on certain diseases that seriously endanger human health. For
example, vitamin P can lower blood lipids, soften blood vessels and increase the toughness and elasticity of blood vessels, so it has the effect of preventing cerebral hemorrhage and also has a certain therapeutic effect on early arteriosclerosis.
Tea leaves have a relatively high fluorine content. Every kilogram of dried tea contains about 75-100 milligrams of fluorine. Therefore, drinking tea regularly can take in enough fluorine to meet the human body's demand for fluorine, which is good for protecting dental health and preventing dental caries.
Tea can also neutralize the acid poisoning caused by a partial diet with too much protein or fat. People in pastoral areas often eat meat and drink milk, and indeed cannot go a day without tea.
In recent years, research has found that the tannins in tea leaves can capture radioactive strontium, thereby preventing and treating certain damage caused by radioactive substances to the human body.
If tea is brewed for too long or left overnight, especially in summer, it very easily deteriorates and turns sour. If it is drunk again, it is harmful to human health.
Drinking hot tea is more beneficial than drinking cold tea. Hot tea entering the stomach can soften food, strengthen the contraction of the stomach wall, promote the secretion of gastric juice, and help digest food. Hot water is easily absorbed by the human body and meets the water needs of various tissues and organs, so drinking hot tea quenches thirst better than cold tea. In addition, the various effective components in tea leaves have a high degree of solubility and high concentration in hot water, so drinking hot tea can fully bring out the effects of tea leaves and help one savor the aroma and taste of tea.
People love drinking tea and are also very particular about tea utensils. The material of tea utensils has a certain
influence on the taste quality of tea. Practice has proved that for brewing tea, finely made pottery tea utensils are best. This is because pottery has certain tiny pores and a certain breathability, moderate heat conduction, and heat preservation suitable for extracting the effective components of tea leaves, so the tea brewed has very good color, aroma and taste. The aromatic oils of tea leaves volatilize when subjected to high heat, so tea leaves should not be brewed with boiling water, and even less should they be boiled.
Tea leaves contain palmitic acid and terpenoid compounds, and these two substances have the characteristic of absorbing other odors. People process tea leaves into scented teas with various aroma types, such as jasmine tea, zhulan tea and magnolia tea, precisely by making use of this characteristic of easily absorbing other odors. Also because tea leaves have this characteristic, tea leaves easily pick up other flavors and cannot be stored together with other things.
However, drinking tea too much or inappropriately can also bring many adverse consequences. The theophylline and tannic acid in tea leaves irritate the gastrointestinal tract. Drinking strong tea too much, especially on an empty stomach, can cause stomach discomfort and stomach pain, and induce and worsen gastric or duodenal ulcers. The tannic acid in tea leaves has an astringent effect and easily causes constipation. Because tannic acid in the intestinal tract can form insoluble iron tannate with iron, affecting the absorption of iron, drinking too much tea can cause anemia. Caffeine and theophylline can speed up the heartbeat, and drinking a large amount of tea poses a risk of inducing and worsening arrhythmia in coronary heart disease patients with premature beats and atrial fibrillation.
The Chemistry in Alcohol
Alcohol is a beverage containing ethanol. More than two thousand years ago, our ancestors already knew how to make alcohol by fermenting grains, potatoes and sweet potatoes
rich in starch as raw materials. In the 19th century, this method spread to Europe. Until now, people are still using it.
Making alcohol by fermenting starch is a very complex biochemical process, and its chemical changes can be roughly divided into two stages: saccharification and alcoholization.
Saccharification stage:
2(C6 H10O 5 ) n + nH 2 O
Starch? ? Enzyme ?
55-60℃
nC12 H 22 O11
Starch Maltose
C12 H 22 O11 + H 2 O ?Maltose? Enzyme?
55-60 ℃
2C 6 H12 O 6
Maltose Glucose Alcoholization stage:
C 6 H 12 O 6
Alcoholization enzyme
28-30 ℃
2C 2 H 5OH + 2CO2 ↑
Glucose Ethanol Many people like to eat glutinous rice wine, and the fermentation process of glutinous rice is the same as the process above. The "wine starter"
used to make glutinous rice wine contains strains such as amylase, maltase and alcoholization enzyme. When making glutinous rice wine, first steam glutinous rice (or good-quality rice) until half-cooked, let it cool, then add wine starter powder and mix evenly,
and ferment at a temperature of 25-30°C. The amylase, maltase and alcoholization enzyme then multiply in large numbers, promoting the production of ethanol. After three or four days, fragrant, sweet and uniquely flavored glutinous rice wine is made.
The various alcoholic drinks we consume contain different amounts of ethanol. Beer contains 3%-5% ethanol, wine contains 6%-20% ethanol, yellow rice wine contains 8%-15% ethanol, and white liquor contains the most ethanol, about 50%-
70%. Because various alcoholic drinks contain different amounts of ethanol, some drinks easily make people drunk and some do not. Beer is made with hops. Beer contains CO2, and CO2 has a weak stimulating effect on the stomach wall and can increase appetite. Beer also contains various vitamins, maltose, protein and phosphate, and is rich in nutrition,
so it has the fine name of "liquid bread." Wine, yellow rice wine and beer, when exposed to air, will turn sour before long, especially in summer
when the temperature is high. Why is this? Because the "degree" of these alcoholic drinks is not high, that is, they contain less ethanol, the acetic acid bacteria in the air that get into the alcohol cannot be killed by the alcohol, reproduce and cause trouble inside, oxidizing the ethanol into acetic acid.
C 2 H 5OH + O 2 ?????? CH 3COOH + H 2 O
White liquor, however, contains more ethanol, and as soon as acetic acid bacteria get in they are killed, so white liquor does not easily turn sour. As the saying goes, the older the wine, the more fragrant. This is because, besides containing ethanol, alcohol also contains fusel oil (a mixture of various higher fatty alcohols) and various organic acids. Fusel oil has an unpleasant smell and feels spicy and irritating to the throat when drunk. During long storage of alcohol, organic acids and fusel oil can slowly react to form various esters with aromatic odors
:
RCOOH+R’OH→RCOOR’+H2O
Higher fatty acids Fusel alcohols Esters Therefore, the longer alcohol is stored, the richer and more mellow its fragrance. For the world-famous Moutai liquor, after it is made,
the wine jars must be sealed and buried underground for several years before being sold. This is very scientifically reasonable.
The Pros and Cons of Drinking Alcohol
On holidays, relatives and friends gather together, using alcohol to add to the fun and drinking heartily. Is drinking alcohol beneficial or not? On this, people have different opinions and there is no agreement on praise or blame. Those who like drinking
praise it extremely, giving it the fine names "nectar" and "jade liquid"; those who dislike alcohol say it is good for nothing, and even denounce it as "causing disease and ruining conduct, disturbing one's nature and harming the body." But many people also believe that one cannot say in general terms whether drinking is beneficial or not; what is important is to pay attention to scientific drinking.
Beer has very high nutritional value and has the fine name of "liquid bread"; yellow rice wine contains 17 kinds of amino acids, and drinking some yellow rice wine is also good for health; wine contains vitamin B1, B2 and C, and also contains vitamin B12 for treating pernicious anemia; white liquor has a relatively high alcohol content and has a relatively strong toxic effect on people, and its nutritional
value is also not as good as beer, yellow rice wine and wine, but it also contains components beneficial to the human body, and is often used to make medicinal liquor and tonic liquor. According to research proof from Harvard Medical School in the United States, drinking no more than 100 grams of white liquor per day can reduce the risk of death in coronary heart disease patients.
Alcohol also has a side that damages health. Whether it is alcohol itself or its metabolite acetaldehyde, both are harmful and not beneficial to the human body. To prevent drinking from harming people, attention should be paid to the following points:
(1) Do not drink excessively. Drinking excessively causes drunkenness (that is, acute alcohol poisoning). In mild cases, one loses composure in speech and behavior, speaks incoherently, laughs and grieves abnormally, becomes dizzy, vomits, sleeps without waking, and delays work; in severe cases, it damages the body, and may even cause death due to cerebral nerve paralysis from severe alcohol poisoning. Therefore, when drinking, it is better to drink less than more, and one must absolutely avoid greedily clinging to the cup. The practice of showing off in front of everyone, egging people on, forcing others to drink more, or showing off one's "great capacity" is not advisable.
(2) Do not drink on an empty stomach. This is because drinking on an empty stomach causes alcohol to directly irritate the gastric mucosa, causing harm
to the stomach. Drinking on an empty stomach also causes alcohol to enter the blood and liver too quickly. The alcohol that cannot be metabolized in time then flows with the blood to the brain and other organs, so drunkenness easily occurs, causing harm to the body's organs. Therefore, when drinking, one should eat some dishes while drinking, or eat part of the staple food, to slow down the speed of alcohol absorption.
(3) Drinking should be selective. It is advisable to choose alcoholic drinks with relatively little alcohol content and relatively many nutritional components, such as beer, yellow rice wine and wine. If drinking white liquor, choose low-degree white liquor of fine quality with no strange taste, no off-flavor and not too strong an irritant effect.
(4) Do not become addicted to alcohol. Modern scientific research proves that alcohol addiction is one of the important causes of stomach and liver diseases. Alcohol can poison all cells, damage many organs of the body, and harm the nervous system, making people slow-witted. If a woman conceives after drinking, she is also prone to have a deformed fetus. The great Tang Dynasty poet Li Bai's superb verses have been handed down through the ages, but because he was addicted to alcohol, he ended up dying after "entering the water drunk to grasp the moon."
Some people are also accustomed to drinking a few cups before going to sleep, seeking drowsiness for a good sleep. In fact, this is a very bad habit. Wang Ying, a medical scientist of the Ming Dynasty, said in Food Materia Medica: "As for wine, people know to abstain from drinking it early, but they do not know that drinking it at night is even worse. Once drunk and full, one sleeps and goes to the pillow. The heat congesting the heart harms the heart and eyes. The night air is converging, and wine is used to rouse it, disturbing one's clarity, taxing the spleen and stomach, causing dampness to stagnate and sores to form, stirring fire and increasing desire, and many people become ill because of this."
By the way, people who are obese are even less suitable for drinking regularly. This is because white liquor and beer are both made from grain, and fruit wine also contains more sugar, so alcoholic drinks generally contain relatively many calories. Beer also has the effect of stimulating the appetite and increasing appetite. At the same time, when drinking, people generally eat a lot of meat and dishes, and salt intake also increases markedly, so nutrition and calories become excessive in the body and cause weight gain.
As everyone knows, obesity is one of the inducing factors of many serious diseases such as coronary heart disease, diabetes and hypertension. If one drinks alcohol for a long time, the result is getting fatter and fatter. Therefore, experts suggest that obese people should drink even less than ordinary people, and must not be greedy for the cup.
In short, drinking alcohol is a common phenomenon in people's lives. To prevent drunkenness from harming the body, one needs to achieve scientific drinking.
The Human Body Trace Elements in the Human Body
Iron A normal adult human body contains 3-4 grams of iron, equivalent to the weight of a small iron nail, accounting for about
0.004% of body weight, of which 60%-70% is combined with hemoglobin in the blood, undertaking the task of transporting oxygen to various tissues and organs and carrying away carbon dioxide. 20%-25% of the iron is stored in the liver, bone marrow, spleen and gastrointestinal mucosal epithelium for use when needed; another about 5% is combined with protein and stored in muscles. Plasma also contains a small amount of iron; the enzymes that maintain normal human activity also contain a small amount of iron. The most common nutritional anemia is caused by insufficient iron supply. Foods relatively rich in iron include animal liver, black fungus and so on.
Zinc The zinc content in the human body is also very small, accounting for about 0.003% of body weight. Zinc has a special role in the human body: it is a constituent component and activator of many enzymes. In addition, zinc is present in the composition of insulin. When the human body lacks zinc, growth and development and sexual maturation will be inhibited, and brain development will also
be affected, and the sense of smell and taste will also become abnormal. For example, some children like to eat cinders and mud, and even eat them with relish, while they are averse to fish, meat and so on. This is "pica" in medicine, and is actually caused by zinc deficiency. It can be treated simply by eating more foods rich in zinc, such as clams and mussels among shellfish foods. Calcium The calcium content in the human body accounts for about 1.5%-2.2% of body weight. Calcium is very unevenly distributed in the human body,
with more than 99% present in bones and teeth in the form of apatite, and the rest of the calcium mainly distributed in body fluids. Calcium in the blood is mainly distributed in plasma, and the calcium content in plasma is related to the phosphorus concentration and protein concentration. In plasma, the normal calcium-phosphorus product is 40, that is, the product of the milligrams of calcium and inorganic phosphorus per 100 milliliters of plasma is 40. When it is less than 30, one may have rickets, and then it needs to be supplemented from food. Calcium ions have the function of inhibiting neuromuscular excitability. In plasma, every 100 milliliters contains 8.5-11.5 milligrams of calcium. When it is lower than 7 milligrams, convulsions will occur.
Magnesium Magnesium in the human body is about 0.05% of body weight, of which 70% is present in bones, and the rest is distributed in various soft tissues and body fluids. Magnesium in the blood mainly exists in blood cells. Magnesium can inhibit nerve excitability, and its effect is even greater than that of calcium. When the magnesium content in the blood increases to 20 milligrams, the central nervous system is inhibited and anesthesia occurs.
Sodium and Potassium Sodium and potassium account for 0.15% and 0.32% of body weight respectively. They exist completely in ionic form in the human body and are present in the body fluids of all tissues. Among them, sodium is mainly distributed in extracellular fluid, while potassium mainly exists in intracellular fluid. Such a distribution indicates that cells have a certain degree of selective permeability. The main role of sodium is to regulate osmotic pressure and acid-base balance in the body, and potassium also has a certain influence. In addition, the acid carbonates and phosphates of sodium and potassium are important buffers in the human body. Together with proteins, they maintain the constant
pH value of body fluids, ensuring the environment necessary for normal physiological functions.
Copper Copper accounts for about 0.00015% of body weight. Its amount is very small, but it is indispensable. If the human body lacks copper, it will also cause anemia just like iron deficiency. This is mainly because copper participates in the blood-forming process in the human body. Copper can promote the conversion of inorganic iron into organic iron, which is beneficial to the absorption of iron. Copper can also prompt iron to enter the bone marrow from storage sites, accelerating the synthesis of hemoglobin. When the body lacks copper, iron supplementation treatment is of no avail. Copper is commonly present in animals and plants, and beans, meat and vegetables are all rich in copper. According to some scientists, trace copper can prevent colds and stop bleeding, and children regularly washing their faces in a copper basin can prevent and treat eye diseases.
Chromium is an element we are all familiar with. Bicycle handlebars, wheel rims, and the steel tubes of tables and chairs are often plated with a layer of chromium on the surface to prevent the steel from rusting and to make it bright and attractive. Chromium is also a trace element essential to the human body, present in larger amounts in childhood and somewhat less in adults. If the human body lacks chromium, it will cause atherosclerosis. General fruit juices, coarse grains, fish, lean meat, and shellfish all contain relatively large amounts of chromium.
Cobalt Cobalt is also a trace element in the human body. It is the main component of vitamin B12, so vitamin B12
is also called cyanocobalamin. It is the only vitamin that contains a metal element. We know that when vitamin B12 is deficient,
it will cause pernicious anemia.
Iodine The human body contains about 20-50 mg of iodine, of which more than 40% is found in the thyroid gland near the throat. It is an important raw material for synthesizing thyroid hormones. Thyroid hormones can enhance the body's metabolic capacity and promote the body's use of sugar, protein, and fat. When iodine intake is low, thyroid hormones cannot be secreted normally, and a person's neck will swell up. This is the disease known as goiter. It is generally believed that iodine deficiency in the environment
and the body's inability to obtain enough iodine from the diet are the main causes of the disease. At present, an important measure is to take iodized salt for treatment.
The Composition and Function of Toothpaste
After people get up every day, the first thing they do is brush their teeth and wash their faces. After a night, the mouth feels very uncomfortable, and there may even be an unpleasant odor. What is the reason for this? It is mainly because the temperature and humidity in the mouth are very suitable for bacterial reproduction, and food residue that has been eaten becomes stuck in the gaps between the teeth and ferments and putrefies. When food putrefies, it also produces acid that corrodes the teeth. Therefore, it is hygienic to brush your teeth and rinse your mouth promptly after eating, and it can also make the mouth feel comfortable.
Brushing teeth requires toothpaste, because food remaining in the mouth can firmly adhere to the surface of the teeth. Only with the help of the abrasive and detergent in toothpaste can the teeth be brushed clean and made bright and attractive. Brushing with toothpaste can also remove bad breath and prevent and treat oral diseases. Why does toothpaste have these effects? This must be discussed starting from the ingredients of toothpaste.
Toothpaste is composed of various inorganic and organic substances, including abrasives, washing and foaming agents, binders, humectants, sweeteners, flavoring agents, and water. In recent years, various drugs have also been added to toothpaste, making many kinds of medicated toothpaste. A good tube of toothpaste, with a gentle squeeze, produces a white, smooth paste. It should have an elegant fragrance, moderate sweetness, a delicate feel, and sufficient foam.
The abrasive is the main component of toothpaste. Commonly used abrasives include calcium carbonate (CaCO3), calcium hydrogen phosphate
(CaHPO4·2H2O), with an amount between 30% and 55%. In order to increase the cleaning effect,
the washing and foaming agent sodium lauryl sulfate (ROSO3Na) also needs to be added, at about 2% to 3%. Toothpaste can
whiten teeth mainly through the action of these two ingredients. The abrasive has a certain friction effect, and the washing and foaming agent has the effect of washing and producing foam. Combined with the action of the toothbrush, they can brush away the dirt on the surface of the teeth and make the teeth as white as jade.
Adding flavorings to toothpaste (such as mint, spearmint, etc.) not only gives a fresh and fragrant feeling during use, but also has a bactericidal effect, removing bacteria in the mouth and preventing the paste from spoiling. To make toothpaste taste good, some saccharin must also be added as a sweetener. In this way, after brushing, the mouth will feel cool and comfortable, with a sweet fragrance.
What kind of toothpaste is best to choose? This depends on each person's situation. If the teeth are strong and white, the choice of toothpaste is generally based on flavor type; if the whiteness of the teeth is not ideal, or if there is tartar and the person likes smoking and drinking tea, it is advisable to use toothpaste with natural calcium carbonate as the abrasive, or phosphorus-containing toothpaste and enzyme toothpaste; people with bad breath should use Maxam or chlorophyll toothpaste; if preventing and treating dental disease, then suitable medicated toothpaste should be chosen according to the symptoms. For example, for dental caries, it is best to use toothpaste containing strontium fluoride or sodium fluoride; for teeth that feel sore and numb when encountering cold, heat, sour, or sweet, anti-acid desensitizing toothpaste can be used; for teeth that often swell, hurt, and bleed, it is advisable to choose Chinese herbal toothpaste with anti-inflammatory and pain-relieving effects, etc. Medicated toothpaste has both the effect of cleaning the mouth and teeth and the effect of preventing and treating dental diseases, so it is generally welcomed by consumers, and its output also ranks first. Our country is rich in Chinese herbal medicine resources and has many varieties. Using them to prepare medicated toothpaste results in mild medicinal properties and few side effects, which is a unique advantage.
Although toothpaste can clean the mouth, if you also develop good hygiene habits, rinse your mouth with clean water after meals, and especially brush your teeth once before going to sleep to remove food remaining in the gaps between the teeth, so as to prevent food residue at night
from spoiling in the mouth and producing odor and corroding the teeth, and to avoid the deposition of tartar, that would be even more hygienic.
Fluorine and Teeth
Fluorine in the human body is mainly concentrated in the bones and teeth, especially the teeth, where the fluorine content reaches 2 parts per ten thousand. Teeth are our chewing organs and play an important role in good health. After food is chewed by the teeth,
it enters the stomach and can then be well digested by the stomach, allowing the nutrients in the food to be absorbed. Moreover, during chewing, the mouth will secrete a large amount of saliva. Under the action of salivary enzymes, food is decomposed and transformed into nutrients that are easily absorbed by the human body. Studies have shown that when eating slowly and chewing carefully, more than 60% of the food will be decomposed. On the contrary, if one eats too quickly, or cannot chew food well because of bad teeth, food enters the stomach, which not only increases the burden on the stomach but also prevents the food from being well digested and absorbed by the stomach and intestines. Many people, especially adolescents and children, only use their teeth but neglect protecting them or protect them improperly, resulting in a sharp increase in dental diseases. For example, dental caries is the most common dental disease.
The main cause of dental caries is unclean teeth. After eating, a lot of residue is left in the gaps between the teeth, especially sugary substances. These residual substances are decomposed by bacteria in the mouth to produce lactic acid:
C 6 H 12 O 6
Lactic acid bacteria
35-45℃
2CH 3 —CH 2 OH—COOH
Glucose Lactic acid Lactic acid can cause the inorganic substances in the hard tissues of teeth, including tooth enamel, cementum, and dentin, to decalcify, and organic
substances to decompose. In this way, the enamel on the surface of the teeth loses its protective effect, making the teeth susceptible to erosion by acidic substances. The teeth themselves have no ability to repair themselves, and over time, cavities gradually form.
To prevent dental caries, one should rinse the mouth after meals, brush teeth before going to bed at night, and develop good hygiene habits. In addition, using anti-caries medicated toothpaste is also very important. This type of toothpaste contains fluorine compounds such as sodium fluoride (NaF), strontium fluoride (SrF), and sodium monofluorophosphate. Fluoride ions (F-) have anti-acid and anti-enzyme effects, can inhibit sugar fermentation and the growth of lactic acid bacteria, and reduce the production of lactic acid; during brushing, fluoride ions can also combine with calcium in the superficial layer of tooth enamel to form poorly soluble calcium fluoride, which has a strong inhibitory effect on Lactobacillus and has a certain preventive and therapeutic effect on dental caries. When using these medicated toothpastes, if the toothpaste can remain in the mouth for a longer time, the effect is even better. However, after use, be sure to rinse away the residual toothpaste in the mouth.
In recent years, many medical prevention experts in our country have proposed preventing dental caries by drinking tea. This is because tea leaves have a strong ability to enrich fluorine from the environment and contain a relatively high amount of fluorine. The people of our country have a traditional habit of drinking tea. It has the effects of cutting greasiness, refreshing the mind, and nourishing the body. Tea leaves contain amino acids, proteins, and inorganic trace elements needed by the human body. However, in terms of their fluorine content, they can both “treat disease” and “cause disease.” Drinking tea in moderation can prevent dental disease caused by a lack of fluorine in the body and is also of great benefit to adolescents and children.
Daily Life Chemical Knowledge in Boiling Water
Boiling water is a small matter in daily life, but little do people know that there is also a lot of chemical knowledge in it.
Tap water in cities and well water drunk in rural areas both contain small amounts of dissolved carbon dioxide and oxygen. When boiling water, as the water temperature rises, the solubility of gases decreases, forming many small bubbles that emerge
from the water. There are also other reasons why bubbles appear when boiling water. When the bottom of the kettle is heated, some water molecules gain energy and become vaporized molecules. As the temperature rises, more and more vaporized molecules form, creating a large number of bubbles that surge out of the water. In addition, water in nature, because it comes into contact with soil and rocks, has dissolved acid carbonates such as calcium bicarbonate and magnesium bicarbonate. These salts are not stable enough and, after being heated, easily decompose to release carbon dioxide. For example:
Ca（HCO3）2CaCO3↓+H2O+CO2↑
When boiling water, a “hissing” sound can be heard. As the temperature rises, the sound goes from small to loud, but when the water is boiled, the sound suddenly becomes smaller again. Why is this?
Experiments have shown that when water is heated from room temperature to 75°C, the temperature difference between the upper and lower layers of water in the kettle is about 1
°C. Within this temperature range, the convection speed of water is very fast, and the temperature of the kettle body can be quickly transferred to the water. As a result, the temperature difference between the kettle body and the water is not large, and at this time there is almost no sound. When the water temperature rises above 75°C, we will hear a “hissing” sound, and as the water temperature rises, the sound becomes louder and louder. This is because the temperature at the bottom of the kettle has already reached above 100°C, and the water temperature inside the kettle is also high. The movement speed of water molecules accelerates, while the convection speed is slow. The temperature difference between the upper and lower layers of water in the kettle is about 3°C. Some water molecules obtain higher energy from the bottom of the kettle, become vaporized molecules, form bubbles, escape the water layer, strike the kettle body, and produce sound. When the water temperature reaches the boiling point, because of the churning of water bubbles, the temperatures of the boiling water and all parts of the kettle body are equalized, and the sound suddenly becomes smaller. As the saying goes: “Water that makes noise is not boiling; boiling water makes no noise.” This is the reason.
After the water is boiled, if it is poured on the ground, the rapid evaporation of water molecules will create an “air cushion” effect, thereby producing a muffled “puff-puff” sound. In this way, one can judge whether the water has boiled.
When calcium bicarbonate and magnesium bicarbonate dissolved in water are heated and boiled, they decompose and produce carbon dioxide, while also forming the white, poorly soluble substances calcium carbonate and magnesium hydroxide:
Ca（HCO3）2CaCO3↓+H2O+CO2↑ Mg（HCO3）2MgCO3+H2O+CO2↑
The generated MgCO3 further undergoes hydrolysis to generate the even more poorly soluble Mg(OH)2: MgCO3+H2OMg(OH)2+H2CO3
Expressed by an overall chemical equation: Mg(HCO3)2Mg(OH)2+2CO2
Calcium carbonate and magnesium hydroxide deposit at the bottom of the kettle and adhere to the kettle walls, forming scale (commonly known as “water alkali”). Scale has very poor heat conductivity. If a kettle accumulates scale, the water is not easy to boil. For every 1 mm of scale thickening, fuel consumption increases by 5%. If large boilers accumulate scale, there is also the danger of causing explosions. How can scale in a kettle be removed? It can be soaked in table vinegar overnight. Acetic acid can dissolve the alkaline substance magnesium hydroxide. The acidity of acetic acid is stronger than that of carbonic acid, so it can make hard scale become loose and very easy to remove. If scale accumulates in a thermos bottle, it affects the heat preservation effect. To remove scale from the inner liner of a thermos bottle, hydrochloric acid, which is more acidic than acetic acid, can be used for a better effect.
CaCO3+2HCl=CaCl2+H2O+CO2↑
Mg（OH）2+2HCl=MgCl2+2H2O2
Talking About the “Gas Tank”
With the rapid development of our country's petroleum industry, in cities, many families have used “gas tanks.” A “gas tank” might seem, as the name suggests, to contain coal gas. In fact, this is not so. What is inside is not “coal gas,” but “liquefied petroleum gas.” “Liquefied petroleum gas” is different from “coal gas.” Coal gas is made from coal, and its main components are hydrogen, methane, and carbon monoxide. After coal gas is produced in a gasworks, it is transported to thousands of households through gas pipelines. Liquefied petroleum gas, however, is a byproduct gas from petroleum extraction or petroleum refining, and its main components are propane, butane, propylene, and butene, etc. People make use of the characteristic that these gases are easy to liquefy, pressurizing and cooling them to liquefy them. After liquefaction, their volume can be reduced to 1/250-300 of the gaseous state, and then they are put into pressure-resistant steel cylinders. In this way, storage, transportation, and use are all very convenient. It can be seen that from the two aspects of source and composition, liquefied petroleum gas and coal gas are different. Therefore, calling the steel cylinder containing liquefied petroleum gas a “gas tank” is a misnomer.
The explosion limit of liquefied petroleum gas in air is 2%-9%. A weak spark can cause an explosion, and when the concentration of liquefied gas exceeds the upper explosion limit, it will burn and catch fire when encountering an open flame. Therefore, when using liquefied gas, it is necessary to frequently check whether each connection part of the stove is leaking. Liquefied petroleum gas is heavier than air. When it leaks, it is not easy to volatilize away, but instead spreads along the ground like water and may stagnate in low-lying places, very easily reaching explosive concentration. If a person stays in a kitchen where liquefied gas is leaking, the combustible gas can not only adhere to clothes and skin, but may even be inhaled into the lungs. Once it encounters an open flame, serious consequences of being burned inside and outside can occur. Liquefied petroleum gas has a strong unpleasant special odor, making it easy to detect. Once a leak is found, doors and windows should be opened promptly for ventilation.
When using liquefied petroleum gas, keep the steel cylinder farther away from the fire source (generally should be more than 1 m away). The steel cylinder should be stored upright and must not be tipped over, to prevent liquefied gas from spilling out. In winter, when the temperature drops, the vaporization speed of liquefied gas slows down. Some people use fire to roast it, which is extremely dangerous. Because roasting will cause the vaporization speed to increase sharply, the gas pressure inside the steel cylinder will rise rapidly, and there is a danger of causing the steel cylinder to explode. Do not pour out the residual liquid in the steel cylinder to keep for other uses. At present, the use of liquefied petroleum gas among urban residents has become relatively common, and fires caused by improper use or equipment failure also occur frequently. Once a fire occurs, the simplest and easiest method is: quickly use a towel, rag, or apron to cover the steel cylinder's guard rail, and immediately close the angle valve, and the fire can be extinguished.
From the perspective of the chemical reaction of liquefied gas combustion:
C3H3+5O23CO2+4H2O Propane
C H + 13 O
4CO + 5H O
4 10
Butane
2 2 2 2
C H + 9 ?burn??point? 3CO + 3H O
3 6 2 2 2
Propylene
C4H8+6O24CO2+4H2O Butene
The complete combustion of 1 volume of propane requires 5 volumes of oxygen. Oxygen accounts for 1/5 of the volume of air, so the volume of air required is about 25 times the volume of propane, while releasing 3 times the volume of propane in carbon dioxide. In the same way, the amount of air required and the amount of carbon dioxide released from burning 1 volume of butane, propylene, and butene can be calculated respectively. Through calculation, it is not difficult to see that the combustion of liquefied petroleum gas requires a large amount of air and produces a large amount of carbon dioxide. If the air plate on the stove is not adjusted well and the air supply is insufficient, the liquefied gas cannot burn completely, and the flame will appear yellow or even emit black smoke. Not only is the heat output low, but toxic carbon monoxide will also be produced. Therefore, good ventilation should be maintained when using liquefied petroleum gas.
It is worth mentioning that liquefied petroleum gas is harmful to household appliances. This is because after combustion, liquefied petroleum gas can produce a certain amount of sulfur dioxide. When sulfur dioxide encounters water vapor and oxygen in the air, it can form highly corrosive sulfuric acid droplets. When these sulfuric acid droplets adhere to household appliances, they will cause them to corrode. Therefore, rooms where stereo systems, tape recorders, and color TVs are placed should be separated from the kitchen as much as possible. Rice cookers, washing machines, and the like should not still be left in the kitchen after use; the water should be wiped dry and they should be moved to another room. Color TVs, tape recorders, stereo systems, and the like should, when not in use, preferably be covered with a relatively dense and thick cloth cover to prevent erosion by harmful gases and dust.
Coal Gas Poisoning
The main component of coal is carbon. When carbon burns, due to different reaction conditions, it can produce two different products. When it burns fully, it produces carbon dioxide:
C+O2=CO2
When it burns incompletely, it produces carbon monoxide:
2C+O2=2CO
Carbon monoxide is a combustible gas. When new coal is added to a stove, or when the air damper below the stove is closed, because the temperature is not high or the oxygen supply is insufficient, more carbon monoxide is produced. Above the coal, one can see flickering blue flames. This is the carbon monoxide formed by combustion.
Carbon monoxide is a toxic gas. After being inhaled into the human body, it can combine with hemoglobin in the blood to form “carboxyhemoglobin.” The binding ability of carbon monoxide with hemoglobin is 200-300 times greater than that of oxygen with hemoglobin. Therefore, after carbon monoxide enters the blood, it is very difficult for oxygen to combine with hemoglobin again. The blood loses its ability to transport oxygen, leading to oxygen deficiency in the body. This is carbon monoxide poisoning, commonly called “coal gas poisoning.”
Calculated by volume, when the content of carbon monoxide in the air reaches 1‰, symptoms of poisoning such as headache and nausea will appear. If the content of carbon monoxide reaches 1%, it can cause death in only 10 minutes. Carbon monoxide is colorless and odorless and not easily noticed by people. The most effective way to prevent carbon monoxide poisoning
is to pay attention to indoor ventilation and air exchange. In winter, many families in northern China use coal stoves for heating. The north wind is piercing and the cold is pressing.
It is necessary to close doors and windows, but we must be alert to this invisible, odorless gas's quiet and very dangerous attack on us. When installing a stove in a room, pay attention to checking whether there are leaks in the stove and chimney, and pay attention to indoor ventilation; when banking the fire, open the stove door and do not let carbon monoxide accumulate indoors. Especially at night, even more attention should be paid to indoor ventilation, and ventilation openings should be left in the windows. If a coal gas poisoning accident occurs, immediately place the patient in a ventilated place, being careful not to let them catch cold. In severe cases, promptly send them to the hospital
for emergency treatment.
Some people say that placing a basin of water on the stove can prevent coal gas poisoning. This statement is incorrect, because carbon monoxide is insoluble in water and cannot undergo chemical changes with water. Water cannot play a role in absorbing carbon monoxide. Some also say that after coal gas poisoning occurs, drinking a little vinegar or sauerkraut soup can detoxify. This is also unreasonable, because carbon monoxide cannot react with the acetic acid in vinegar or the lactic acid in sauerkraut, and cannot eliminate the harm of carbon monoxide to the body.
The development of modern science and technology has given victims of coal gas poisoning a savior - hyperbaric oxygen. In hospitals, giving patients oxygen at very high pressure can not only rapidly relieve the patient's symptoms of oxygen deficiency, but also accelerate the dissociation of carbon monoxide from hemoglobin. According to measurements, under 1 atmosphere of pressure, the half-life of carboxyhemoglobin is 520 minutes, while under 3 atmospheres of pressure, breathing pure oxygen, its half-life is only 23 minutes. How can the pressure of oxygen be increased? This requires a sturdy, sealed special room. Oxygen is pressed in so that the oxygen pressure in the room reaches 1, 2, 3, or more atmospheres. The patient breathes freely in this hyperbaric oxygen environment. This sealed room is like a ship's cabin, so it is called a hyperbaric oxygen chamber. According to clinical observations, without hyperbaric oxygen chamber treatment, the mortality rate of coal gas poisoning is 11%-15%, while with hyperbaric oxygen chamber treatment, the mortality rate of severe coal gas poisoning is 4%-6%. It is reported that using hyperbaric oxygen chamber treatment once
saved the life of a coal gas poisoning patient who had been in a coma for 36 days.
Industrial Manufacturing The Manufacture and Pollution of Firecrackers
Do you know what the black powder in firecrackers is made from? Why do firecrackers explode? And why can fireworks emit colorful colored light?
As the saying goes, the ingredients of black powder are “one saltpeter, two sulfur, three charcoal.” Yes, but you should know that the “one, two, three” here means that the ingredients of black powder are, first, potassium nitrate, second, sulfur, and third, charcoal, but the mass ratio of these three ingredients is not 1:2:3. In fact, black powder is prepared according to the following proportions: potassium
nitrate 75%, sulfur 15%, charcoal 10%. When black powder is ignited, potassium nitrate decomposes and releases oxygen, causing sulfur and charcoal to burn violently and release
a large amount of heat, generating a large amount of gas. Ignite
2KNO3+3C+SK2S+3CO2↑+N2↑ Because the rapid expansion of gas volume causes an explosion, the potassium sulfide particles produced by the explosion form thick
smoke. In some firecrackers, the black powder is divided into two layers. The gas produced by the first explosion, by means of the reaction force of the air, pushes the other part high into the air, where it emits a crisp explosion sound. This is the “double bang.” The raw material for making fireworks is also black powder. The difference is that, in order to make fireworks emit colored light, other chemicals are added. For example, adding strontium carbonate can emit red light, and adding barium nitrate emits green
light.
With the development of environmental science, people are paying more and more attention to the environmental pollution caused by setting off firecrackers. The environmental pollution caused by setting off firecrackers is mainly manifested in two aspects:
Chemical pollution The chemical composition of firecrackers is very complex, mainly potassium nitrate, charcoal, and sulfur. According to their functions, the components of firecrackers
can be divided into oxidants (potassium nitrate, potassium chlorate, etc.), combustible materials (sulfur, charcoal powder, red phosphorus, magnesium powder, etc.), and flame colorants [such as barium salts (flame appears green), sodium salts (flame appears yellow), silver salts
(flame appears red), etc.]. After the gunpowder in the firecracker is ignited, these substances undergo a series of complex chemical changes, produce a large amount of gas, and release a large amount of heat, thereby causing an explosion and producing sound.
When firecrackers explode, they release harmful or toxic gases such as carbon monoxide, carbon dioxide, sulfur dioxide, and nitrogen oxides, and produce particulate smoke and dust such as carbon particles and metal oxides. These gases and smoke fill the air, making the air turbid and suffocating. They also irritate the mucous membranes of the human respiratory tract, damage lung tissue, and even induce respiratory diseases.
Physical pollution A large number of firecrackers being set off will produce intense noise and pressure shock waves. According to measurements, the sound level unit can
reach 137 decibels. The results of near-field sound level measurements of individual firecrackers are: Flash Thunder 130 decibels, Big Green Whip 125 decibels, both exceeding the noise emitted by anti-aircraft machine guns. These noises have a very strong stimulating effect on the human nervous and auditory systems. In addition, firecracker noise also has the characteristics of impulsive sound, that is, rapid onset and high peak value, so it can cause palpitations and deafness, aggravate the condition of patients with hypertension, heart disease, and neurasthenia, and is especially unfavorable to children, the elderly, and the weak. In addition, the other harms brought by setting off firecrackers are also very great. Accidents such as causing fires, injuring fingers and eyes, and even causing permanent disability also frequently
occur. After firecrackers explode, a large amount of shredded paper scraps are scattered in the streets and alleys, also affecting environmental sanitation.
Colorful Neon Lights
After night falls, in bustling downtown areas and shop windows, neon lights shining with bright colors can be seen everywhere, very beautiful and moving.
The world's first neon light was invented in 1910 by the French chemist Claude. At that time, the lamp was filled with neon gas. We Chinese like to call this kind of lamp “neon light.”
A neon light is a gas discharge light source. At both ends of the lamp tube, two electrodes made of iron, copper, aluminum, or nickel are installed, and a small amount of gas is filled into the tube. After electricity is applied, under the excitation of the electric field, electrons in gas atoms at energy levels close to the nucleus are excited to farther high energy levels. But electrons at high energy levels are unstable and will quickly and automatically jump back to their original energy levels. At the same time, they release the energy obtained from the power source during excitation in the form of electromagnetic wave radiation. When the electromagnetic waves radiated by the gas atoms happen to be within the range of visible light, our naked eyes can see a certain color of glow. This is the luminous principle of neon lights.
For different gas atoms, the atomic structure is different, and the energy released when electrons jump back to their original energy levels after being excited is also different. The frequency of the corresponding radiated electromagnetic waves is therefore also different, so the colors of the glow we see are each different. For example, neon gas produces red light, argon can emit light blue light, and helium gas can emit pale red light. If mercury vapor is filled in, it can emit green-purple light. If the inner wall of the lamp tube is coated with fluorescent substances, more colors can be obtained. For example, if the tube wall is coated with blue fluorescent powder and filled with neon gas, it produces pink; if filled with argon and mercury vapor, it produces bright blue. And if the tube wall is coated with green fluorescent powder and filled with argon and mercury vapor, it produces emerald green light, etc. As long as appropriate gases, appropriate fluorescent powders,
and lamp tubes bent into various shapes are selected, all kinds of colorful neon lights can be made.
Wonderful “Dry Ice”
Everyone knows that ice is formed by condensed water, but there is another kind of ice unrelated to water, and that is “dry ice.” Dry ice is formed by condensed carbon dioxide gas.
If carbon dioxide is put into a steel cylinder and pressurized, it can become a liquid like water. If the temperature is lower, it can become a white solid just like winter snowflakes. This is dry ice. However, it is finer than snowflakes, and one must never pick it up directly with hands, because its temperature is as low as -78.5
°C, which will freeze hands. After frostbite, black spots appear on the skin, and after a few days it begins to ulcerate. In Texas, USA, a strange thing once happened. One day, several geological exploration team members used a drilling machine to drill into the ground. When they drilled very deep, suddenly, underground gas sprayed out from the drill hole at a pressure of more than 900 kg, and immediately a large pile of white “snowflakes” accumulated at the mouth of the drill hole. This was dry ice. Curious exploration team members touched it with their hands. As a result, their hands either blistered or turned black. Deep in the strata, some places gather a large amount of carbon dioxide, which becomes liquid under the huge pressure of the earth's crust. When the drilling machine reaches that place, the high-pressure gas rapidly sprays out, and the liquid carbon dioxide rapidly vaporizes,
absorbing a lot of heat, and part of the carbon dioxide becomes dry ice. When dry ice vaporizes, the heat it absorbs is twice that of the same mass of ice. Using it as a refrigerant, the low temperature obtained
is much better than that obtained with ordinary ice. The carbon dioxide gas produced by the vaporization of dry ice also makes it harder for bacteria to survive, so its preservative effect is also better than that of ordinary ice.
Dry ice has the ability to “summon wind and call rain.” Using an airplane to scatter dry ice into the air, it suddenly vaporizes, taking a large amount of heat from the cloud layer, making the cloud layer cold to -40°C. After each kilogram of dry ice vaporizes, it can form 100 quadrillion small ice crystals in the cloud layer. When the surrounding cloud and mist encounter the small ice crystals, they condense on them, become large water droplets, and fall as raindrops. From the time the dry ice is scattered, in less than 20 minutes, a good rain falls. Soon the rain passes and the sky clears. The thirsty crops, in the warm sunshine and moist air, flourish again.
On the stage of movies, television, and drama, one can see fairies dancing gracefully in a heaven filled with swirling clouds and mist, and the all-powerful Sun Wukong riding clouds and mist in a sky of rolling white clouds. This is another outstanding “performance” by dry ice. Scattering some dry ice on the stage, it rapidly vaporizes, absorbs heat, the air temperature suddenly drops, water vapor condenses, and a large amount of white mist forms. On the stage, the wonderful scene of rolling white clouds and swirling mist then appears. In addition, using dry ice to represent flying waterfalls and flowing springs among high mountains and steep ridges, or special scenes such as river embankment breaches and flooding, also has quite good effects.
A Miracle from the Soil - About Antibiotics
Antibiotics, in a wide variety of names, are now commonly stocked medicines in hospitals, pharmacies, and even households. People use them to overcome various ferocious pathogenic bacteria threatening human health. Not long ago, diseases such as bacterial pneumonia, meningitis, and pulmonary tuberculosis caused by once rampant and almighty streptococci, tubercle bacilli, and other pathogenic bacteria were still regarded by people as incurable diseases with certain death. Since the advent of antibiotics, miracles of “curing the disease as soon as the medicine is applied” have appeared in those dying patients, saving many patients from the brink of death. At first, they were “miracle drugs” more precious than gold, but today they can be bought for just ten or twenty cents. They are not only widely used to sterilize and treat diseases, but can also be used as feed additives for poultry and livestock, reducing diseases in poultry and livestock and stimulating livestock to grow larger and fatter. Do you know that these miracle drugs were not gifts from God? They truly “grew naturally” on Earth, and to find and produce them, people paid how much arduous labor. Now this family is still constantly joined by new members, becoming a new force suddenly rising in the pharmaceutical industry.
One
Like many other medicines, the use of antibiotics was much earlier than their discovery. That is to say, before people understood their true appearance, they already knew how to use them. As early as more than two thousand years ago in China's Han Dynasty, people already knew how to use mold on tofu to treat sores and boils on the skin. More than 1,400 years ago, in the Northern Wei Dynasty, Jia Sixie's Essential Techniques for the Welfare of the People recorded Shenqu for treating diarrhea and dysentery. The Danqu mentioned in The Exploitation of the Works of Nature more than 300 years ago was the earliest antibiotic medicine.
The discovery of antibiotics began with penicillin, and this is still a very interesting story.
At the end of the 17th century, Leeuwenhoek, the old gatekeeper of the Delft city government in the Netherlands, was the first person in the world to use a self-made microscope to see bacteria invisible to the naked eye. From then on, humanity unveiled the secrets of microorganisms. But
by the mid-19th century, after studying a large amount of material, French biologists pointed out for the first time that certain bacteria invisible to the naked eye were the culprits causing infectious diseases. At the same time, they also discovered that some substances could inhibit bacteria, pointing out that it was precisely “life inhibiting life.” In 1889, a French chemist first used the word antibiotic to name this type of substance.
As early as 1897, Ernest Duchesne injected an intermediate cultured from Penicillium G fungus into mice suffering from plague, confirming that antibiotics could inhibit infectious diseases in animals. Although the experimental mice were saved, his discovery was not seriously and deeply explored, and it was soon forgotten. Two years later, someone else used a crude antibiotic called pyocyanase to treat diphtheria, but these experiments could not be continued for various reasons.
It was not until 1927 that British bacteriologist Alexander Fleming, while studying staphylococci, had his specimen accidentally contaminated by soil containing humus, thus growing a green mold. Wherever these green molds reached, the staphylococci disappeared without a trace. Around the green mold appeared a blank area - called an inhibition zone. Fleming did not ignore this accidental phenomenon, but carefully observed and seriously studied it. He finally confirmed that this Penicillium must have secreted a substance
with powerful bactericidal ability. He and his assistant inoculated the Penicillium into broth culture medium and let it multiply vigorously. Then they carefully filtered these liquids, and finally obtained a small bottle of clear filtrate. He found that even if these filtrates were diluted several hundred times, they could still kill staphylococci and pneumococci, and even the ferocious streptococci were subdued by it. He called this substance secreted by Penicillium “penicillin.” The English transliteration is penicillin.
However, Fleming's discovery and research did not attract enough attention. This is because the amount of penicillin contained in these filtrates was really too small. If a patient used this penicillin to treat disease, at least tens of thousands of milliliters of filtrate would be needed, which would require as much culture liquid as a small pond. Therefore, this experiment could only remain in test tubes.
Eleven years passed. Howard Florey of Oxford University in England, while searching for new drugs to treat bacterial diseases, read Fleming's paper, which aroused great interest in him. He cooperated with chemist Ernst Chain and began the arduous work of manufacturing penicillin. Chain racked his brains and improved the method of purifying penicillin, but after improvement this work was still arduous and tedious. All the culture liquid in a culture tank taller than a person could only extract penicillin the size of a needle tip, and it was also so “delicate.” Slight heating would decompose it; a slight change in pH would make it ineffective. During their research process, World War II broke out. Even the large amount of glassware needed for experiments was in short supply. They had to use all usable containers, even people's chamber pots, to culture Penicillium.
After several months of effort, they finally produced a small pinch of brown-yellow penicillin powder. They chose a policeman with sores at the corners of his mouth, infected by bacteria and already near death, for the test. After he was injected with penicillin, the pus in the patient's wound decreased significantly, and his consciousness began to clear. However, due to the body's metabolism, penicillin disappeared quickly in the body. In just one hour, all the penicillin that had not taken effect was excreted cleanly in the urine. At this time, Florey had to give the patient penicillin by drip while collecting every drop of the patient's urine and sending it to Chain, so that he could extract from the urine penicillin far more precious than gold. By the fifth day, the patient's condition had basically improved. Unfortunately, by then the penicillin had been used up, and there was not even penicillin the size of a needle tip left. The bacteria that were about to disappear rapidly multiplied in geometric progression and attacked the still very weak patient again, finally taking his life. Although this experiment ended in failure, it allowed people to see the dawn of victory.
In order to increase the yield of penicillin, it was necessary to find Penicillium strains with high yield and improve the culture liquid. After World War II broke out, thousands upon thousands of wounded and sick soldiers were carried from the front lines to rear hospitals for treatment. Florey and his companions also came to the United States, far in the rear, to continue their scientific experiments. In 1942, some pilots received a strange order requiring them to collect a small piece of soil near airports around the world and bring it back to the United States. It turned out that Florey and the others wanted to screen high-yield strains from soil samples from various places. Soil collected from around the world, and even moldy food and melon and fruit peels, were concentrated in the laboratory. In the end, they found the ideal strain from a moldy cantaloupe peel from a Peoria market - strain No. 832. At the same time, corn flour and lactose replaced the previous broth and glucose nutrient liquid, increasing the yield tenfold. In early 1943, the penicillin produced was only enough to treat a dozen patients. Two years later, penicillin had become a drug that could be bought in ordinary pharmacies. In 1944, American bacteriologist Waksman screened Streptomyces that could kill tubercle bacilli from tens of thousands of soil specimens, and separated and purified
streptomycin from them. Scientists also obtained chlortetracycline after studying 3,400 soil samples. They collected tens of millions of soil specimens before isolating oxytetracycline. From then on, the family of antibiotics continued to grow.
Two
To determine from tens of thousands of various mold samples which molds have an inhibitory effect on certain bacteria and to screen out these molds is indeed meticulous and arduous work.
First, countless soil samples from which fungi can be cultured and which have bactericidal value must be systematically screened. Usually, a diluted soil suspension is poured into Petri dishes with nutrient medium. After culturing for several days, all microorganisms multiply, and colonies of various colors appear in the culture dishes. They can be identified and isolated one by one. Then, they are transferred to slanted agar for further culture.
How can you determine whether the mold you have obtained can secrete antibiotics that kill pathogenic bacteria? This requires further culturing of the mold obtained above. Place the small-mouthed container holding this mold upside down in a large culture dish. The culture dish contains culture liquid inoculated with pathogenic bacteria. At this time, the antibiotic multiplies in the small-mouthed container and penetrates from the stopper into the culture dish. If it has the effect of killing that pathogenic bacterium, a clear circle will appear around the mouth of the bottle where the pathogenic bacteria cannot survive. This is called an inhibition zone. Using this method, scientists have already discovered thousands of antibiotics, but only a few hundred have relatively good characteristics, and fewer than 50 are currently widely used.
Agar is an ideal material for culturing bacteria. It is a polysaccharide extracted from seaweed. When it is heated and melted into a liquid, it can be evenly mixed with various nutrients, and after cooling it becomes a jelly-like solid. Therefore, it can both be mixed with various nutrients according to the needs of bacterial reproduction and allow bacteria to reproduce in fixed areas without mixing, making them easy to separate. In order to increase the contact surface with air, liquid agar is often placed at a slant, and after solidifying it becomes slant agar.
The next step is to test molds with cultivation potential and determine the activity spectrum of their secretions - used to determine their disease-resistant effect on pathogens. These pathogens include bacterial yeasts, rickettsiae, and some things called viruses that are actually not viruses. Antibiotics, as the name suggests, are mainly used to resist bacteria. General antibiotics are powerless against true viruses.
Once we have determined the activity spectrum of the antibiotic we have cultured, we can compare it with the spectra of currently known antibiotics to see whether it is a new antibiotic. If this antibiotic is newly discovered and does indeed have significant disease-fighting effects, it can be further isolated and purified. To be on the safe side, its toxicity to humans and livestock must also be tested, because antibiotics often have side effects. Only then can it be used in industrial production. To increase antibiotic yields in industrial production, two approaches can be taken: one is to change the composition of the culture medium; the other is to replace the original low-yielding strain with a new high-yielding variety. High-yielding varieties can be obtained from samples in nature, or by exposing the strain to ultraviolet light, X-rays, or chemical mutagens to
induce mutation.
III
Once molds with bactericidal ability and high yield have been screened out, they can be used to produce antibiotics. At present, antibiotics are still mainly produced by fermentation. The entire production process is carried out in several stages.
Take the production of chlortetracycline (chlorotetracycline) as an example. First, purification is carried out, and viable spores are preserved in sterile soil. Then culturing is done in test tubes containing agar rich in nutrients. The colonies obtained from this step of propagation are then washed into flasks containing culture medium for expanded culturing. The culture medium usually contains starch, sucrose, or other carbohydrates that can provide carbon, as well as substances that can provide nitrogen, such as casein, fish meal, and corn steep liquor. These nutrients are gradually consumed during the mold's growth. Sometimes, in order to incorporate specific active groups into the antibiotic, certain additives containing these chemical groups are also added to the flasks. For example, in penicillin production, adding phenylacetic acid can introduce a phenyl group into the penicillin molecule, thereby producing the more active penicillin G.
The next step is to transfer the culture from the flasks to larger bottles for further expanded culturing. Then the culture from the large bottles is inoculated into fermentation tanks for production. The containers used at each step must be strictly sterilized, and the fermentation tanks and the pipes within them must also be sterilized with high-temperature, high-pressure steam, so as to ensure the purity of the product.
The main production still takes place in fermentation tanks. During the reaction process, the temperature and pH inside the tank must be strictly controlled. The pH value is usually controlled by adding acid or alkali. Inside the tank there is a spiral cooler, through which cooling water flows to control the temperature inside the tank and prevent the large amount of heat generated during fermentation from making the temperature inside the tank too high and killing the mold. In order to make the temperature inside the tank uniform, a stirrer should be installed in the tank for mechanical stirring. In order to prevent the large amount of foam produced during fermentation from isolating the solution from the air and causing the mold in the solution to lack air and “suffocate”, sometimes an antifoaming agent such as sterile lard must also be added. After the fermentation process is completed, the product can be obtained from the mold or from crystals in the culture liquid. Generally, several grams of antibiotic can be produced per liter of fermentation liquid.
IV
Although the benefits of antibiotics are obvious and indisputable, there are still some issues that must be noted, namely side effects and the development of resistance. The side effects produced by antibiotics range from mild skin rashes to severe anemia, and even shock and death. For any miracle drug, the danger it poses to the patient should be offset by its benefits to the patient. Some drugs have relatively severe side effects, and these drugs are usually used only to treat infections that carry greater danger.
Another side effect is causing mutation in the body's cells. Although each cell has a different threshold for mutation. For some cells, because their mutation threshold is relatively high, some antibiotics may never be able to cause them to mutate. However, some cells may be caused to mutate by antibiotics while other cells are still in a normal state. Precisely because every cell in the body that comes into contact with antibiotics has the possibility of mutation, the larger the dose of antibiotic, the greater the possibility of cell mutation. Therefore, when using antibiotics, overdose must be avoided.
Another side effect of antibiotics is the emergence and development of drug-resistant bacterial strains. Some antibiotics are more likely than others to induce bacteria to develop resistance, and some bacteria are particularly sensitive to these antibiotics. In fact, the problem is very complex; bacterial resistance can be transmitted, not only among bacteria of the same species,
where resistance can be passed from one generation to the next, but sometimes resistance can also be transmitted among different species of bacteria. For example, a common harmless bacterium in the intestinal tract may transmit genetic information to a dangerous pathogenic bacterium, enabling it to develop resistance. The way to deal with this side effect is to develop new antibiotics. However, bacteria will likewise develop resistance to these new drugs.
At the same time, some doctors are worried about the current phenomenon of overuse and abuse of antibiotics. Henry Simmons and Paul Stolley published an article in the Journal of the American Medical Association, pointing out that antibiotics are currently used as the most common drugs in clinical treatment, and about 15% to 20% of prescriptions include antibiotic drugs. They found that in some prescriptions, the use of antibiotics was superfluous. In quite a few prescriptions, antibiotics were prescribed merely to prevent bacterial infection. In fact, only in children with viral middle ear inflammation must bacterial infection be prevented, because bacterial infection may lead to death, and only then is it absolutely necessary to use antibiotics for prevention. Simmons and Stolley believe that the vast majority of antibiotics prescribed for preventive purposes are superfluous. One source points out that about
20% to 30% of cold patients were prescribed antibiotics by their doctors, even though antibiotics are completely ineffective against colds.
In one journal issue, an article signed C·T Cunningham pointed out that antibiotics on prescriptions are often requested by patients over the phone from doctors, in the belief that this can achieve rapid treatment. Because if patients go to see the doctor themselves for a detailed examination, it will take up some of the doctor's valuable time. In the United States, some doctors simply use the telephone to brush off patients. The author believes that this irresponsible medical attitude should be criticized. Antibiotics should be used only after a careful examination of the patient confirms that a certain antibiotic is uniquely effective against the pathogen causing the patient's infection.
Simmons and Stolley say that the most dangerous thing is the emergence of drug-resistant bacteria. For Gram-negative bacteria, this will more noticeably alter the ecological habits of such bacteria. The emergence of these resistant bacterial bodies inevitably leads to the need for larger doses of antibiotics or broad-spectrum antibiotics to deal with them. Some sources indicate that whenever increased doses of antibiotics are used in hospitals to prevent surgical infections, this inevitably leads to an increase in the incidence of Gram-positive bacterial infections. Therefore, Simmons and Stolley suggest that hospitals establish advisory committees to supervise antibiotic use.
However, Simmons and Stolley's statistical data and the conclusions drawn from them have been opposed by many people. Some doctors in the American Medical Association, abbreviated AMA, agree that further research should be conducted before drawing conclusions about antibiotic use. In fact, in the mid-1970s, the AMA decided to examine the situation of antibiotic use in hospitals. At the same time, it also drafted a plan to collect information on antibiotic use and to educate doctors to use antibiotics in appropriate amounts.
V
Although antibiotics are usually used as medicines to treat disease, people were surprised to discover during use that they have the effect of promoting the growth of many animals. This was discovered during World War II, when, due to a shortage of fish and other animal protein feed, plant protein had to be used to replace animal protein in raising poultry and livestock. But Western farmers were very unaccustomed to this. Although scientific analysis proved that the amino acid composition contained in plant protein was basically the same as that of animal protein, plant protein could never make poultry and livestock grow as
fast as when fed animal protein. Logically speaking, animal protein must contain something lacking in plant protein. Now, it has been clarified that this mysterious thing in animal protein is an animal protein factor called APF.
Scientists at the U.S. Department of Agriculture discovered that APF exists in the livers of animals, and APF was also found in cow manure, chicken manure, and even chicken manure from chickens that had never been fed animal protein. However, Western chicken houses use wire mesh and raise chickens on elevated wire floors, not letting them peck freely on the ground. Obviously, APF may be produced by their own bodies.
But what puzzled scientists was why chickens themselves produced this growth-stimulating substance and then excreted it as useless manure. The question was answered: it turned out that this substance was not produced by the chicken's body, but was produced in the warm chicken house by bacterial fermentation in the manure.
Unfortunately, because the amount of APF is too small, isolating it is extremely difficult. In the end, a research group at Merck & Co. and a British research group isolated it using less-than-ideal methods. They
isolated from the liver the long-sought anti-pernicious anemia factor, namely B12, and they wanted to determine whether vitamin
B12 was the active ingredient in APF. They already knew that APF exists in the liver. Finally,
through experiments, they confirmed that B12 can promote animal growth.
In order to manufacture B12, they investigated various fermentation methods and found that this vitamin is produced by several
organisms, including Streptomyces, which had already been used to produce streptomycin. Before long, they used Streptomyces fermentation to grow pure B12 for human use, and less pure BB12 for feeding animals.
Other manufacturers then sought the potential market for this vitamin and looked for their own new methods of synthesizing it. For example, Lederle Laboratories used the chlortetracycline-producing Streptomyces aureofaciens to
produce B12. Subsequently, they discovered another astonishing effect: chickens fed this antibiotic
culture grew faster than those simply fed BB12. Clearly, there must be something in this impure substance
that can promote animal growth. Finally they concluded: trace amounts of antibiotics, such as chlortetracycline, even as little as a few parts per million of body weight, are sufficient to promote animal growth. Later, pharmaceutical manufacturers found that antibiotics such as penicillin, oxytetracycline, and bacitracin had the same effect.
Today, antibiotics have become an indispensable animal feed additive and are added to animal feed.
In 1973, the United States alone sold 88.4 million dollars' worth of antibiotics for use as such feed additives. But to this day no one has clarified how antibiotics stimulate animal growth. It is generally believed that this is because antibiotics change the composition of E. coli that normally inhabit the animal body. Another theory holds that antibiotics reduce the likelihood of animals getting sick. The basis for this theory is that poultry and livestock are constantly fighting various pathogens. Even if these pathogens have disappeared from the bodies of healthy animals, new pathogens may attack the body at any time. Precisely because antibiotics reduce the probability of poultry and livestock getting sick, they grow faster and stronger.
Regardless of which mechanism is involved, the results of using antibiotics are indisputable: they enable poultry and livestock to reach market weight with less feed. For example, if pigs are fed a small amount of antibiotics, they need only 85% of the feed required by pigs not fed antibiotics to reach the same slaughter weight, and the former grow 30% faster than the latter. The same effect is seen when feeding chickens and calves. Here is a question worth raising: if antibiotics are continuously added to feed, will this result in the emergence of resistant bacteria that attack poultry and livestock, thereby making antibiotics ineffective when treating sick poultry and livestock? However, to date,
no sign of this side effect caused by the use of antibiotics in feed has been found. At present, the benefits of adding antibiotics to feed clearly outweigh the potential risks.
Antibiotics are a widely used and continuously developing new class of drugs. As long as we use them cautiously, maximizing their strengths and avoiding their weaknesses, they will certainly play a tremendous role in the fight against disease.
Chemical Knowledge About Animals
Why Spiders Are Not Caught in Their Own Webs
This simple question raised in the title of this article is probably difficult for anyone to answer.
Since the oil crisis occurred, the call to “learn from nature, learn from the natural world” has grown stronger day by day. Indeed, many scholars have turned their attention to nature and to the natural world. They hope that by clarifying natural phenomena and understanding the behavior of animals and plants existing in nature, they can then apply the principles and laws within them, so as to achieve the goal of learning and imitation. This is like a breath of fresh air blowing into a mind stuffed with knowledge; the scope of knowledge is expanded. For humanity, is this not very valuable?
The main conceivable reasons why spiders are not caught in their own webs are:
(1) The spider's body structure is simply like that.
(2) The spider can secrete from its body a substance that keeps it from being caught.
(3) The spider's eyes see very accurately, so it does not get caught in the web.
(4) There is some mystery in the spider web. The answer is simple, but in order to arrive at the correct answer, we must first spend some words explaining
how the spider web is constructed. Because the key to the question is hidden in the structure of the web. A completed spider web is composed of three kinds of
threads: radial threads, adhesive threads (sticky threads), and coiled foothold threads, and this kind of web is a structure of very high regularity. After the web is completed, the spider comfortably keeps watch at the center of the web, quietly waiting for prey to arrive. Once the prey
is caught by the adhesive threads, the spider can go directly along the radial threads to the place where the prey is stuck. The reason the spider is not caught in the web is that it walks only on the radial threads that have no adhesive, and it does so swiftly and skillfully. But people had never thought of this. In any case, saying vaguely that “the web can only catch prey” is inappropriate and unconvincing. Because no matter what it is, as long as it walks where there is no adhesive, it likewise will not be caught.
You might say that the spider's eyes are especially sharp, but that is wrong, because the spider's eyes are actually highly nearsighted. Since it is nearsighted, why can it see so clearly when prey is stuck? For such a question, the answer can be found in the highly regular web. Because although the spider is nearsighted, it can rely on the regularly constructed web to correctly judge the direction of the web's vibrations when the prey struggles, so that it can go directly to the place where the prey is stuck. Conversely, if the prey does not struggle at all, the spider will not come out either. If a person is caught in a web, there is no need to worry. For example, on the island of Madagascar there is a kind of spider that can catch small birds. When a person is caught in this clever web, as long as they do not grab and move about wildly, they can take the opportunity to walk away.
Someone might also raise this question: to catch prey in the web when it is struggling violently, would the spider, which takes the shortcut without turning, also not be caught by the web bearing adhesive? There is no need to worry about this at all, because the spider has a clear head. The adhesive threads are not fully coated with adhesive; the
adhesive exists as small droplets one by one. Although when the adhesive is first applied by the spider it is full and abundant, after a period of time it shrinks into spheres. When prey touches these large droplets, adhesive sticks to its body, and the more it struggles, the more sticks. Even so, when the spider walks over, almost no adhesive sticks to its body, and even if some can stick, it is very slight.
The various adhesive tapes sold on the market today are almost all surface-adhesive tapes coated with glue over the entire surface; there are almost no tapes with dotted adhesive like spider webs.
In addition, an unnecessary doubt may also arise: what happens if a spider is caught by some other kind of adhesive? At this time, in order to walk, the spider can, when necessary, secrete from its claws toward the front part of its limbs an oily substance of unknown composition (another account holds that the oily substance is first secreted from the spider's mouthparts and then applied to the limbs). In this way it can produce a kind of “mold-release” effect on the adhesive. In short, the spider itself will not be caught.
Because the adhesive on the web is a concentrated aqueous solution of an amino acid polymer, it can be dissolved away by rainwater when it rains. Therefore, spiders do not spin webs on cloudy days and when it rains.
Why Silkworms Only Eat Mulberry Leaves
Here is a recipe: citral 10 mg, inositol 5 mg, β-sitosterol 5 mg, potassium hydrogen phosphate 10 mg, isoquercitrin 3 mg, silicon dioxide 40 mg, sucrose 30 mg, cellulose 700 mg. Add these ingredients to 3 mL of 2% agar to make a jelly-like food.
This is a recipe for agar jelly food prepared for silkworms, published in 1962 in the British journal Nature
. At a glance one can see that it is an artificial food containing no protein or other nutritional essentials, made purely from chemical substances.
This recipe was proposed by some people after research in order to explain the question “Why do silkworms only eat mulberry leaves?” They wanted to use it to prove that, as long as these several components extracted from mulberry leaves are present, silkworms can eat food prepared from this recipe just as they eat mulberry leaves.
In 1959, someone proposed a hypothesis: silkworms eat mulberry leaves because the attraction of scent drives them to approach, then special substances stimulate the chewing behavior, and finally, under the synergistic action of several substances, continuous feeding occurs. This hypothesis has already been proved by the following experimental facts.
Take a piece of mulberry leaf and soak it in ether to dissolve out the scent and color. After such treatment, silkworms no longer approach it. However, if the above ether extract is dripped onto filter paper, silkworms will move toward the filter paper, but they do not chew it. Yet silkworms do chew the mulberry leaf residue remaining after ether extraction. Then this mulberry leaf residue is extracted with hot methanol, and the extract is added to agar jelly. At this time, although traces of extensive chewing by silkworms can be observed, no traces of defecation can be observed. However, when the mulberry leaf residue remaining after hot methanol extraction is also added to agar jelly, the silkworms not only chew well and swallow well, but also excrete feces.
Thereafter, further research was carried out to separate from the ether extract (ME), the hot methanol extract (Mw), and
the mulberry leaf residue (R) remaining after extraction with these two solvents various factors such as the attraction factor, the chewing factor, and the swallowing factor.
Silkworms can eat agar jelly containing mulberry leaf powder very well, and at this time each silkworm can excrete about 20 pieces of silkworm droppings overnight; likewise, silkworms can also eat agar jelly containing ME, Mw, and R at the same time very well, and can likewise excrete about 20 pieces of silkworm droppings. On this basis, the following experimental plan was proposed:
extract the various effective components in ME, Mw, and R, and modify them appropriately.
What was isolated from ME was citral - a terpenoid essential oil - and β-sitosterol; what was isolated from Mw
was isoquercitrin - a flavonoid pigment - and inositol, as well as sucrose; finally, what was isolated from R was potassium hydrogen phosphate, silicon dioxide, and cellulose. After doing this, agar jelly food containing the various components in the above recipe was prepared, and silkworms could eat this food just as they eat mulberry leaves.
The above research was carried out starting from the understanding that “why silkworms eat mulberry leaves” is because mulberry leaves contain feeding-stimulant substances. But the question “why silkworms only eat mulberry leaves” cannot yet be considered fully explained from this aspect alone. Because from the composition of the several basic foods that silkworms eat, it can be seen that they are not components unique to mulberry leaves, since other plant leaves also commonly contain these substances. Therefore, since we emphasize “only eat mulberry leaves,” we must start from a different standpoint from the above and introduce a hypothesis of “whether feeding-inhibitory factors exist.” That is, we do not consider whether plant leaves other than mulberry leaves contain substances that stimulate silkworm feeding, but consider only that the reason silkworms do not eat other leaves is that these leaves contain feeding-inhibitory substances.
Based on the above hypothesis, it can be considered that “silkworms only eat mulberry leaves” because the various components in the above recipe that exist in mulberry leaves are not only exactly balanced in quantity, but also do not contain the feeding-inhibitory substances commonly present in the plant kingdom. Only by explaining it from these two aspects can it be considered relatively appropriate.
In addition to the above conclusions obtained from analyzing the composition of mulberry leaves, research can also be carried out from the side of the silkworm itself. Silkworms perceive scent through their antennae; if the antennae are removed, they cannot perceive nearby mulberry leaves. Taste is perceived by the maxillae near the mouthparts. According to reports: silkworms whose maxillae have been removed can eat cherry tree leaves.
Later, through electrophysiological research, it was found that on the silkworm's antennae there are cone-shaped sensilla that can perceive scent. In addition, among several sensilla on the maxillae, Ss-I contains a sugar receptor that perceives sucrose and a receptor that perceives inositol; in the Ss-II sensillum, there is a receptor extremely sensitive to bitter substances, which can be considered a receptor cell for feeding-inhibitory substances.
In addition, the part called the maxillary palp is also a sensory organ of the silkworm. It is estimated that more receptor cells will certainly be identified in the future. These different sensilla of the silkworm can perceive not only feeding-stimulant substances but also feeding-inhibitory substances. It is the result of the synergistic action of these perceptions that constitutes the control mechanism of feeding behavior.
The Secret of Why Crabs and Shrimp Change Color When Heated
Hairy crabs, mud crabs, soldier crabs, snow crabs, swimming crabs, prawns, shrimp, lobsters?? countless kinds of crabs and shrimp generally have their shells turn red (though with differences in depth) when heated or cooked. If such reddened shells are soaked in acetone, the red pigment in the shell will seep and dissolve into the acetone, dyeing the acetone a beautiful orange-red, and the shell will accordingly fade and become lighter. The main pigment component obtained by the above extraction method can already be made into crystals by a simple method, so as
early as 1938, Kuhn and others applied this method to isolate this pigment from the eggs of a kind of lobster and named it astaxanthin.
Animals containing astaxanthin are not limited to crabs and shrimp; many other crustaceans also adorn themselves with astaxanthin. However, some small crustaceans mainly contain crustacyanin, and some crabs contain pterorhodin (butterfly red pigment) in their bodies, and the amount of this pigment is far greater than astaxanthin.
The chemical structures of these pigments are all similar to the main component of the pigment found in edible carrots -
β-carotene. A class of pigments derived from β-carotene is called “carotenoids.” They are distributed abundantly and widely in nature. Carotenoids are the main component constituting the pigments of crustaceans, but the molecules of this carotenoid component all contain a characteristic functional group, the carbonyl group, and are therefore called “ketocarotenoids.”
If ketocarotenoids isolated from organisms are dissolved in different solvents, various colors from orange-red to deep red (sometimes purplish-red) can appear. They show absorption maxima at light wavelengths between 450
and 510 nanometers. The reason the shells of crabs and shrimp turn red when heated is that the true color of the ketocarotenoids is revealed.
In this way, the question “why do crabs and shrimp turn red when heated” becomes such interesting and basic questions as “why do the shells of crabs and shrimp containing orange-red to red ketocarotenoids appear to be a completely different color when alive or fresh?” and “why does this color also show various changes with different species of crustaceans?”
The body color of living crustaceans is not entirely the same, due to differences in species and differences in environment. And this difference is because the pigment exists in pigment cells in the skin, also called chromatophores. Under external stimuli, these cells can exhibit different hormone secretion states, thereby causing the cells to expand or contract, and this expansion or contraction will cause the body color to change. However, regardless of the body color of living crustaceans, as long as they are soaked in formalin or heated, they will likewise turn red.
It is known that carotenoids in organisms are often bound together with specific proteins in a special way, that is, they exist in the form of pigment proteins. However, this binding cannot cause significant changes in the absorption peak they show in the spectrum. Therefore, the color of carotenoids in solution and the color of carotenoids bound to protein are not very different, and in this case the color likewise will not show obvious changes due to heating. Even if some color change can be seen at this time, it is merely a change of the pigment cells from a contracted state to an expanded state, so carotenoids will not cause color change.
In fact, the pigment proteins extracted from the shells of crustaceans can, in most cases, absorb light of longer wavelengths than carotenoids bound to protein, and even in extreme
cases can appear blue-green.