What to Do When Dracaena Leaves Turn Yellow? Find the Cause and Master 5 Techniques
Although Dracaena is a very precious ornamental plant, if you do not pay attention to its care, yellowing leaves may appear, which not only affects the beauty of the plant's shape but also indicates health problems, so it is important to find the cause promptly and solve the problem
Although Dracaena is a very precious ornamental plant, if you do not pay attention to its care, yellowing leaves may appear, which not only affects the beauty of the plant's shape but also indicates health problems, so it is important to find the cause promptly and solve the problem. So what should you do when Dracaena leaves turn yellow? The editor has put together several techniques commonly used by flower growers.
What to Do When Dracaena Leaves Turn Yellow
1. Lack of Light
Dracaena is a plant that likes sunlight, but many flower growers worry that exposure to direct sun will cause the leaves to wilt, so they keep it in a dark place. However, because the light is too dim and it lacks sunlight, the leaves cannot carry out photosynthesis and turn yellow.
What to do: Let the Dracaena receive sufficient light and avoid keeping it in a dark environment for a long time. It is best to let it receive 3-4 hours of sunlight every day, especially in winter when more light is needed.
2. Too Little Watering
Dracaena is fairly drought-tolerant, but it cannot go without water for a long time. Too little watering can cause many problems. Besides yellowing leaves, it can also lead to pests and diseases, soil compaction, and other issues, and yellowing leaves are one of them.
What to do: Replenish water in time but do not let water accumulate. In later care, water scientifically; for methods, you can refer to the detailed introduction in how to water Dracaena. However, during the rainy season, pay attention to watering appropriately, and for outdoor cultivation, stop watering.
3. Nutrient Deficiency
The nutrients contained in the soil are limited, and some flower growers rarely fertilize and do not change the potting soil often, so the Dracaena will have some leaves turn yellow due to a lack of necessary nutrient elements during growth.
What to do: What should you do when Dracaena leaves turn yellow due to nutrient deficiency? At this time, do not apply fertilizer with too high a concentration. Instead, replace the potting soil to make the soil more fertile and loose, and at the same time apply dilute fertilizer water once a month in later care.
4. Over-Fertilization
If the Dracaena develops new leaves that are thick and uneven on the surface, while old leaves wither, turn yellow, and fall off, flower growers can consider whether there has recently been frequent fertilization or too high a concentration. Over-fertilization can also cause yellowing leaves; this is one of the common problems in growing many plants.
What to do: When over-fertilization occurs, increase the amount of watering to reduce the fertilizer concentration and let some fertilizer flow out through the drainage holes. If the situation does not improve significantly, replace the soil, and afterward be careful not to over-fertilize.
5. Dry Air
Although Dracaena is a tropical plant, it likes a humid environment. If the air is relatively dry, it can cause yellowing leaves, dry leaf tips, and other problems. Many plants that like humid environments can develop this problem, such as spider plant, copper coin grass, and so on.
What to do: Increase the air humidity around the Dracaena and pay attention to the weather. When the humidity is low, spray some water on the plant's leaves to prevent the air from becoming too dry. In addition, pay attention to air circulation; maintaining ventilation can prevent the humidity from becoming too low.
The Wonder of Turning a Blind Eye - Stories of Chemistry in Life
The Wonder of Turning a Blind EyeFire and Humanity
The invention of fire was approximately 500,000 BC. In the cave where Peking Man lived at Zhoukoudian, China, very thick ash and some fossilized animal bones and ash burned by fire were once discovered, which proves 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 to defend 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 were both results of the use of fire. Regarding the question of fire, in the late 17th century and early 18th century, due to the rapid development of Europe's 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 objects contain phlogiston, and that substances that cannot burn do so because they lack phlogiston. This erroneous theory dominated the chemical world for nearly a hundred years and hindered people's exploration of the essence of fire. It was not until 1777, when Lavoisier discovered oxygen, that the phlogiston theory was completely overturned and the mystery of combustion was revealed. Lavoisier submitted the scientific report "General Considerations 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 life: people use the heat released by combustion to smelt metals; in household life, to boil water, cook, and keep warm; use the combustion of diesel and gasoline to drive trains, cars, airplanes, and tractors; use the explosion caused by the rapid combustion of gunpowder to blast mountains and mine ores and dig tunnels; in the military, to 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 huge space rockets into space.
Combustion can benefit humanity, but it can also bring disasters to humanity. As everyone knows, combustion can cause fires. In 1987, a particularly severe forest fire in the Greater Khingan Mountains of our country burned for 28 days, with a fire area of 1.01 million hectares, causing enormous losses to the lives and property of the state and the people. In coal mines, the rapid combustion of methane or coal dust can cause serious explosion accidents. In flour-producing 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 all depend on 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.
For any fire to occur, three conditions must be present, namely combustibles (such as paper, wood, cotton, oils, etc.), combustion-supporting substances (such as air), and ignition sources (such as cigarette butts, embers, etc.). If these three conditions are separately controlled or isolated, a fire cannot occur; if one of these conditions is removed, a fire will likewise not occur. Every combustible has its own ignition point and spontaneous ignition point. For example, the ignition point of wood is generally 250-350°C, and its spontaneous ignition point is generally around 350°C; the ignition point of cotton is around 150°C, and its spontaneous ignition point is about 400°C; the ignition point of gasoline is -58-10°C, and its spontaneous ignition point is between 255-530°C; the ignition point of cooking oil is between 140-300°C, and its spontaneous ignition point is between 350-570°C. If the temperature reaches the ignition point of these combustibles, 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 spontaneous ignition point of a combustible, it will catch fire even without encountering an open flame. Therefore, the most important measure for preventing fires is to store combustibles properly, especially to avoid contact with fire sources.
Water has good fire-extinguishing performance and is the most common, most economical, and most convenient extinguishing agent. Water has a very large heat capacity; 1 liter of water rising 1°C can absorb 1 kilocalorie of heat. Therefore, pouring water on ordinary burning materials such as firewood and wood can rapidly lower the surface temperature of the burning material below its ignition point; at the same time, after 1 liter of water is heated and vaporized, it can produce more than 1,700 liters of water vapor. Water vapor can dilute the concentration of combustible gases and combustion-supporting gases in the burning area and can prevent air from entering the burning area, thereby extinguishing the fire.
However, not all fires can use water as an extinguishing agent. For example, oil fires and electrical fires. The specific gravity of oil is smaller than that of water, and it is mutually insoluble 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 and easy-to-operate fire extinguisher is called a foam fire extinguisher. It is a cylindrical red steel cylinder with a nozzle, handle, and top cover. Inside the steel 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 will spray out to extinguish the fire. This is because after the foam fire extinguisher is turned upside down, the sodium bicarbonate solution and aluminum sulfate, which were originally stored separately, can mix together and undergo the following chemical reaction:
6NaHCO3+AL2（SO4）3=3Na2SO4+2Al（OH）3↓+6CO2↑
After the chemical liquid in the foam fire extinguisher reacts, it can produce gelatinous aluminum hydroxide, which, together with the added foaming agent and under the action of the carbon dioxide produced by the reaction, 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 carefully 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 bottle increases, and the steel cylinder may explode. 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 extinguishing fires of different natures, corresponding firefighting equipment must be selected. When talking about fire, people naturally think of matches. Small and exquisite matches ignite with a single strike,
it is the simplest way for people to make fire. Before the invention of matches, humans could only obtain fire by drilling wood or by violently striking hard flint (whose main component is silicon dioxide, SiO2) with 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 said to be a giant match, because it was made from a wooden stick more than 1 meter long, with a large lump made by mixing potassium chlorate, sugar, and gum arabic stuck to 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 comes into contact with concentrated sulfuric acid, a chemical reaction occurs, producing a very reactive chlorine dioxide, and chlorine dioxide reacts with sugar, causing combustion. This kind of match was large and heavy, very inconvenient to carry, also required carrying dangerous sulfuric acid at the same time, and was expensive, so it was not popularized.
By the early 19th century, Swedes had discovered friction matches. Friction matches were small, compact, and convenient and quickly became popular in various countries. The head of this kind of match was coated with sulfur, 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 could ignite just by being rubbed on a wall, tabletop, or shoe sole. After white phosphorus was ignited, with the help of strongly 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 ignite, and white phosphorus is a highly toxic substance; accidental ingestion of 0.1 grams 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 attached to 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 woods such as pine or poplar, and the front end was also thoroughly soaked with paraffin and rosin to make the matchstick easy to ignite. This kind of match only ignites when rubbed on the matchbox. It is neither toxic nor likely to cause fire, so it is called “safety match”. This kind of match quickly replaced friction matches and sold all over the world, right up to the present.
It has been more than two hundred years since the birth of matches. Over these more than two hundred years, through continuous improvement by people, many matches with special properties have been made, making the match family increasingly prosperous. Such as windproof matches, welding matches, multiple-use matches, and so on.
In daily life, people deal with fire every day; however, when using fire, one must prevent fire. Neglecting safety, being careless, or lacking fire prevention knowledge can 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 adviser Zhang Liang sent someone to write seven large characters by the Wujiang River with honey - “Xiang Yu, the Hegemon of Chu, will cut his own throat at Wujiang.” Ants immediately gathered from all directions to feed. When Xiang Yu retreated to the Wujiang River after defeat and saw these striking seven characters formed by many ants, he thought the “mandate of Heaven” had ended, and sighed with emotion: “Heaven is destroying me; why should I cross?” With a boat available he did not cross, and cut his own throat with his sword. 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 plate glass. People glued a metal plate behind the plate glass to make a relatively ideal mirror. Things are precious when scarce; at that time mirrors were astonishingly expensive. When Queen Mary of France, Marie de' Medici, married, the Republic of Venice gave her a mirror as a gift. The mirror was only as large as a book, yet it was worth 150,000 francs!
Later people came up with a method: using mercury (quicksilver) instead of a metal plate. This kind of mirror had very good brightness and also low cost, and ordinary people could afford it. However, mercury vapor is toxic, and workers often suffered mercury poisoning accidents when making mirrors, taking 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: 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, choose glass without bubbles, grind it flat, wash it clean with alkali, then take silver nitrate and prepare
it into a solution of a certain concentration, add an appropriate amount of ammonia water, and 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 deposited on the glass plate, making a mirror. To prevent the silver from darkening and peeling off, finally paint the back of the mirror to protect it.
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 in this way, thermos bottle liners are also
silvered in this way. Everyone knows that sugar is sweet; it is the 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 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, its huge molecules split apart, forming smaller molecules, and combine 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 only 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 - sawdust, rice straw, wheat straw, and many agricultural by-products containing cellulose - can certainly 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%), and continuously stir and heat. After 4-5 hours, add water to dilute, then add lime milk to neutralize and filter. At this time the filtrate 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, heat the filtrate to concentrate it, 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! Russian Fahlberg was a researcher at Johns Hopkins University in the United States and also a chemist,
he was busy in the laboratory all day. That day, an experiment produced a result, and he happily took out the pencil inserted in his pocket and wrote the experimental result in the experiment record.
When he was putting the pencil 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 instructed 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 guests and host 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 are aromatics??” “This is a chemical term.” Fahlberg felt he could not explain clearly, so he casually took 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 time, Fahlberg's wife was just serving steaming hot 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, talking about how that strange sweetness had come about. “I did not add any sugar!” his wife explained. Fahlberg walked 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 edges of the plates. After returning to the sofa, he actually raised both hands, first licked 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 found a sweet-tasting spot on the edge of the plate. This was where his fingers had held the plate. And his hand had once held the pencil used in the laboratory. This showed that the sweetness of the pencil had been picked up in the experiment.
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 single-mindedly to researching this topic, and finally extracted from coal tar a sweet-tasting substance - saccharin.
Experiments proved that the sweetness of saccharin is about 500 times that of edible sugar. Struggle and hard battle finally gave Fahlberg the reward he deserved. In 1879, Fahlberg obtained the patent for the invention of 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. When talking about vinegar, it makes people recall some wonderful pleasures. Adding vinegar to cold mixed dishes makes them tasty and stimulates saliva endlessly. When cooking fish-flavored shredded pork or sweet-and-sour spare ribs, adding vinegar enhances color, aroma, and taste, greatly increasing your appetite and keeping it open. A bottle of aged vinegar will add much luster to a family's holiday banquet.
As the saying goes, the seven things for opening the door are oil, salt, firewood, rice, sauce, vinegar, and tea. It can be seen that vinegar has an extraordinary relationship with people's daily life. And with the development of the organic chemical industry, vinegar has become an important chemical raw material indispensable to human development at every moment. Below let us slowly tell it from ancient times to the present.
In ancient times, vinegar was called xi cu or bitter wine, all with the “wine” radical, showing that vinegar and wine have an indissoluble bond. As a condiment, when edible vinegar began cannot be verified. But among the people there has always been handed down the legend of “Du Kang made wine, and 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, drawing river water to soak distiller's grains. It was the height of summer, and he fell into a drowsy dream. After waking, according to what he remembered in the dream, he opened the cover after 21 days, and indeed a fresh scent rushed to the nose, sour with a hint of sweetness. Heita then took “twenty-one days” and added a “west” character, calling this sour water “vinegar.” This is the origin of vinegar.
The traditional fermentation method of brewing vinegar is still used today. Its key points are: after steaming grains cooked, saccharify them through koji, and the alcoholic product obtained after alcoholic fermentation is not distilled, then mixed with bran, grain chaff, acetic acid yeast, etc., and kept
at around 40°C to continue fermenting, obtaining edible vinegar.
Amylase
(C H On + nH O ?starch?enzyme? →nC H O6 10 5 2 6 12 6
Starch Glucose
C H O alcoholic fermentation enzyme? →2C H OH + 2CO
C 2 H 5 OH + O2
Acetic acid bacteria
40 ℃
→CH 3COOH + H 2O
Acetic acid
In addition to acetic acid (containing 5%-6%), edible vinegar 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 1,700 years ago. During the Three Kingdoms period, the famous doctor Hua Tuo used mashed garlic and half a bowl of vinegar to cure a passing patient, prompting him to vomit out a roundworm, immediately relieving the suffering of a blocked throat that prevented swallowing. 26 years ago, when influenza viruses raged across the world, causing tens of millions of people to be bedridden, some workers in the photography industry, because they used dilute glacial acetic acid solution when fixing negatives and photos, were spared infection by the disinfecting and sterilizing effect of acetic acid vapor. From then on people used acetic acid to prevent influenza. Some take 5 grams of table salt and stir-fry it over gentle heat, put in 15 grams of tea leaves and stir-fry until slightly scorched, add 200 milliliters of water and boil, and the resulting filtrate with 10 milliliters of edible vinegar added becomes a good medicine for treating diarrhea in children. Edible vinegar here plays an astringent role. It is recorded that 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 fragrance vanillin. In 1890, the German chemist Hoimann 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 respectively. At that time, when showing films, the greatest fear was burning film and causing fire, because the film base was made of flammable cellulose nitrate ester. Cellulose acetate ester is not easy to burn and not easy to fade, and after its appearance it immediately replaced cellulose nitrate ester, becoming an important raw material for photographic negatives and motion picture film.
Acetic acid is the earliest organic acid produced by people, and also the first completely organic synthesized compound that scientists produced starting from elements. 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 production of industrial acetic acid also developed from the initial methods of distillation of edible vinegar and fractional distillation 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 that the most promising production method should be the direct synthesis of acetic acid from methanol and carbon monoxide CH3OH+CO→CH3COOH, but because some major technical problems have not yet been completely solved, this method is still in the exploratory stage.
Chemistry in Sports
Friends, do you know that in the exciting and pleasing world of sports, chemistry is everywhere.
For thousands of years, the torch has always been a symbol of light, courage, and power. Since the 11th Olympic Games, every opening ceremony has held a rather solemn “torch relay.” Who makes the torch shine with dazzling brilliance? It is flammable organic matter. Butane gas and kerosene are both commonly used torch fuels:
2C4H10+13O2 ignite 8CO2↑+10H2O
Butane The lightweight torch of novel design developed by Chinese chemistry experts has a flame up to about one meter high. Even on a clear day, it is still clearly visible from more than two hundred meters away, and it still burns brightly in heavy rain. It added much color to the 11th Beijing Asian Games.
In fierce football matches, we often see players fall on the lawn. At this time the team doctor hurries forward, uses a small spray bottle, chh! chh! sprays a few times on the injured part of the player, then repeatedly rubs and massages, and before long the injured player unexpectedly charges back onto the field full of energy. What miracle drug is in the small bottle? This is ethyl chloride (CH3CH2Cl), a colorless, easily volatile organic substance 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 an athlete's injured part, because it rapidly volatilizes, the temperature of the skin surface suddenly drops and sensation decreases, thereby producing the unique effects of pain relief and local anesthesia.
At the stadium, surrounding the emerald green football field are very striking reddish-brown athletic tracks in circles. This kind of track is laid with the newest synthetic material - plastic. Commonly called a “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 particles, 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 excellent results.
Different athletes also have different requirements for the materials of sports shoes. For this reason, designers have adopted the newest chemical materials to design sports shoes with various properties, which are quite favored by athletes. Basketball and volleyball players need shoes with a certain bounce, so they choose cis-polybutadiene rubber with very good elasticity as the sole; football players require shoes that can adapt to fast attacks and fast stops and are solid and durable, so they use very high-strength polyurethane rubber as the sole material and install polyurethane anti-slip studs; track and field athletes require shoes that are soft and elastic, so high-elasticity isoprene rubber soles were designed, satisfying the athletes' requirements.
Why does a starting pistol produce white smoke after being fired? The powder in the gunpowder paper contains substances such as the oxidizing agent potassium chlorate and the smoke-producing agent red phosphorus. The high temperature produced by friction causes potassium chlorate to rapidly undergo decomposition reaction:
High temperature
2KClO3
temperature 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 very easily absorbs water in the air to form acid mist, so the timekeeper sees a faint 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 absorption and can increase the friction coefficient between the palm and the equipment, thereby enabling athletes to grip the barbell tightly and create excellent results.
After the magnificent stadium is decorated with brown glass, it is beautiful and elegant, giving people a quiet and refined impression. Brown glass is a heat-absorbing, heat-insulating glass that can absorb infrared rays. It contains trace oxides such as iron, cobalt, and selenium, and the infrared rays it transmits are only 1/4 of those of ordinary glass. 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 when walking into the stadium 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 made by mixing hard rubber and plastic and pressing them; 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 made of ultrafine nylon fiber and polyurethane fiber can make athletes swim faster?? However, the abuse of chemical substances has also brought disaster to the pure world of sports. Do you remember, at the 24th Seoul Olympics, when Canadian sprint star Ben Johnson defeated American sprint star Lewis with a 100-meter time of 9
seconds 79, and broke the men's 100-meter world record he himself had held, the entire stadium boiled over. People excitedly shouted his name like welcoming a hero, cheering and paying tribute to him. But a few days later, the Olympic organizing committee announced a shocking piece of news: Johnson had taken banned drugs during the competition, the new world record he created was canceled, and his gold medal was taken back. Johnson used improper means to deceive international public opinion and sullied the Olympic spirit, and he was condemned and punished.
Most banned compounds are organic compounds, complex in composition and numerous in types. At present, the banned drugs stipulated by the International Olympic Committee fall into five major categories and 99 kinds. They are: synthetic steroids, narcotics, stimulants, β-blockers, and diuretics. 70% of the stimulants taken by athletes are synthetic steroids.
Taking steroids can increase muscle, enhance endurance, adapt to high-volume training and accelerate recovery after training, and achieve better results in competition. But such drugs are very harmful to the body. They not only damage the liver but are also a cause of liver cancer, and can cause cancerous changes in the urinary system and bring harm to the heart and blood vessels. To safeguard 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 humanity for thousands of years to “spread clouds and make rain” has now become reality. And the scientist who first realized artificial rain was the outstanding American physical chemist Irving Langmuir.
Irving Langmuir was born on January 31, 1881, in Brooklyn, New York City, USA. Langmuir was extremely interested in natural science and applied technology from childhood. When young, he already had a great ideal: to realize artificial rain and free humanity from the fate of depending on the sky for food.
Langmuir deeply understood the mood of farmers hoping for rain during dry seasons. Facing the farmers' gazes 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 understood the mystery.
It turns out that water vapor on the ground rises, meets cold, and condenses into masses, which is “cloud.” The tiny ice points in clouds are only about 0.01 millimeters 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 rapidly condenses on the surface of the ice crystals, making the small ice crystals grow into snowflakes. Many snowflakes stick together to become snowflakes, and when the snowflakes are 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 area with a temperature above 0°C, they melt into water droplets and rain falls.
However, having clouds does not necessarily mean rain. This is because the 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 constrained people's experiments and research on artificial rain. Because in cloudy weather, raising dust all over the sky is easier said than done.
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 filled in 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 continuously adjusted the temperature and added various dusts to conduct experiments.
One day in July 1946, the sun blazed overhead and the heat was unbearable. Langmuir was conducting an experiment under great tension when suddenly the refrigerator stopped cooling due to some equipment failure, and the temperature inside could not be brought down. He decided to use dry ice to lower the temperature. Solid carbon dioxide has a very large heat of vaporization: 87.2 calories per gram at -60°C. Under normal pressure it can rapidly convert to gas, absorbing heat from its surroundings and producing a cooling effect that can bring the surrounding temperature down to about -78°C. Just as he put some dry ice into the freezer compartment of the refrigerator, an utterly wondrous scene appeared: tiny ice particles swirled and danced within the compartment, fine snowflakes fell from above, the whole compartment was piercingly cold, and the artificial cloud turned into ice and snow.
Analyzing this phenomenon, Langmuir realized that dust is not absolutely necessary for rainfall, and that dry ice has a unique ability to condense water vapor, acting as "seeds" - ice crystals or ice nuclei - in clouds. The drop in temperature is also one of the important factors that turns water vapor into rain. He continually adjusted the amount of dry ice added and changed the temperature, and found that as long as the temperature dropped below -40°C, there was a chance of success in artificial rainfall. Langmuir's dry-ice cloud-seeding method was a breakthrough discovery in artificial rainfall research; it broke free from the shackles of old ideas. Interestingly, this breakthrough invention was achieved inside a refrigerator in the heat of 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 direction, an airplane soared up and flew above a sea of clouds. The test personnel scattered 207 kilograms of dry ice into the cloud sea, just as farmers sow seeds in a wheat field. Thirty minutes later, a fierce wind suddenly arose and torrential rain poured down upon the earth. The first artificial rainfall experiment was a success.
Langmuir opened a new era of artificial rainfall. Based on the theory of ice crystal nucleation in supercooled cloud layers, scientists further discovered that silver iodide (AgI) and other substances could be used as "seeds" for artificial rainfall. Moreover, in terms of effectiveness, silver iodide is better than dry ice. Silver iodide can be scattered on the ground and, using rising air currents, drift up into cloud layers in the sky, making rainfall induction simpler and easier than with dry ice.
"Artificial rainfall" operations as a new type of "weather weapon" in warfare were seen repeatedly. During the Vietnam War, the "Ho Chi Minh Trail" leading from Cambodia to Vietnam was heavy with traffic; combat supplies from abroad supporting the Vietnamese people in resisting the American imperialist aggressors were continuously sent to the front through this sole route. But torrential rains and massive floods often occurred there, breaking bridges, destroying dikes and dams, and leaving large numbers of transport vehicles struggling on muddy mountain roads; traffic was greatly affected, and the destruction was no less severe than bombing. At first the Vietnamese side was completely unaware of these sudden rainstorms. Later, after investigation through many channels, they learned that this was a secret weather operation approved and carried out personally by U.S. President Johnson and lasting 6 years - namely, the United States conducted "artificial rainfall" operations over that route.
"The sky has foreseeable winds and clouds" - its meaning lies not only in "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 destroyed 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
China 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, there are painted patterns in alternating red and black, proving that our ancestors already knew how to paint with colored pigments more than five thousand years ago. According to research, the black pigment used at that time was carbon 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 even more brilliant than red ochre. The chemical composition of cinnabar is mercury sulfide (HgS). Because of its gorgeous color and lasting permanence, it has always been highly treasured by painters. The seal ink used for stamping seals on calligraphy and paintings is also made from cinnabar. In ancient calligraphy and paintings, because of their great age, the paper has discolored and yellowed, yet the seals on them are still vividly red.
The gracefully dancing flying apsaras in China's famous Dunhuang murals can be called world art treasures. But the faces and skin of those heavenly maidens are mostly grayish-black - what a strange thing!
It turns out that the grayish-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; where it was applied, it could truly be called dazzlingly white. Because it was corroded over a long period by trace amounts of hydrogen sulfide gas in the air (hydrogen sulfide is produced when coal burns and when animals and plants decay), it gradually changed from white to grayish-black.
2PbCO3·Pb（OH）2+3H2S=3PbS↓+2CO2↑+4H2O
(White) (Black) In museums, oil paintings on display gradually lose their luster and the white areas darken after a long time, for the same reason. 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 galleries in Europe. In Italian museums, many famous paintings from the Renaissance are treasured. Visitors were astonished 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 an ore 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 a long period 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 function": it can fairly accurately predict changes in the weather. Local people discovered that if the pale red color at the clothing of the figures in the mural gradually fades and turns into brilliant blue
color, then even if the sky is at that time shrouded in mist and covered with dark clouds, one can go out without rain gear with complete peace of mind; conversely, if the blue at the clothing of the mural figures turns pale red, it foretells that it may be going to 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 water of crystallization appears red, while anhydrous cobalt dichloride appears blue. Whenever rain is approaching, the humidity in the air rises, and the blue anhydrous cobalt chloride in the painting absorbs moisture, forming pale red hydrated cobalt dichloride; and when the water of crystallization in the hydrated cobalt dichloride in the pigment gradually evaporates and the blue color returns, that is proof that the air is dry and the sky is about to clear.
proof. Dry or heat
CoCl2·6H2O CoCl2+6H2O Pale red Blue
An English architect added some cobalt dichloride to the cement used for whitewashing an exterior wall, ingeniously combining the principle of color change with the principle of color, and created a landscape painting whose "season" changes with the weather. Whenever the autumn air is crisp and the weather is dry, the cobalt dichloride hydrate loses its water, changing from red to blue; blue and the yellow in the watercolor pigment are complementary and become green, presenting to people the vibrant spring colors that have already passed. And when spring and summer arrive, the humidity is greater, cobalt dichloride absorbs moisture again, changing from blue to red; red and yellow merge into one, and the landscape painting once again brings people a patch of orange unique to autumn, symbolizing harvest.
color.
Applications of Color
A Colorful Life
Why is the sky blue? Why are trees green? We live in a brilliantly colorful nature, and color is a very important part of composing nature. Color not only affects the lives of almost all animals, but also has a great influence on human life. Just imagine: if everything around you were only monotonous colors, then you would certainly feel gloomy, depressed, and utterly lifeless. All kinds of 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 the retinal cells. The wavelengths of light that humans can see 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 400-500 nanometers can activate the blue pigment, producing the sensation of blue; light with a wavelength of 500-600 nanometers can activate the green pigment, producing the sensation of green; light with a wavelength of 600-700 nanometers activates the red pigment, producing the sensation of red. All other colors are merely the result of mixing these three basic colors. Mixing all 3 colors together produces white, and when all 3 colors are absorbed, the result is black.
The ability to distinguish color is not limited to humans. Many fish, amphibians, reptiles, birds, and even insects all have the ability to distinguish colors, only 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 animal 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 color of surrounding plants.
The peppered moth in England is an example of adapting to the environment and choosing protective coloration. The specimens of this moth that 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 brilliant colors is to frighten other animals. Animals that are poisonous or unpleasant-tasting often use light or bright colors together with easily recognizable patterns and markings to warn carnivorous animals not to eat them. Carnivores, in turn, avoid them based on these colors, so the colors benefit both parties. 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, the male robin and peacock use the beautiful colors of their feathers to attract females. It should be pointed out here that in fairy tales and legends passed down among humans, as well as on the stage, beautiful peacocks or other beautifully colored animals are often used to represent pretty girls, but in nature the situation is often the opposite: male animals are generally beautiful and moving, while female animals often appear plain and ugly.
Camouflage with color plus pattern is even more effective. Among these, various butterflies are the most outstanding. Some butterflies have eye-like patterns on their wings. When they spread their wings and fly, they frighten birds and other carnivorous animals that see them. Some tropical fish also use bright colors to scare off "sea overlords" such as sharks. The pale yellow dead leaf butterfly, when its wings are folded together, looks very much like a dry leaf, and can greatly confuse its enemies. In short, it is precisely by using color to adapt to the environment during evolution that animals have survived.
Humans and Color
The history of human use of color can be traced back to 150,000 to 200,000 years ago, when primitive people smeared red or yellow clay on their bodies to frighten wild beasts and show their beauty to their companions. Primitive people also burned bones and teeth to make black pigments, or used 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 obtained from the roots 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 and 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 all the rage in the West. This beautiful red-purple color is closely related to indigo. It was prepared from the oxidized secretions of some mollusks in the eastern Mediterranean. According to reports, one (28.4 grams) of this dye required 240,000 sea animals as raw material. In short, this pigment was extremely expensive, costing about 7,500 dollars each. Therefore, people often associated this pigment with nobility. Thus, in English there is the phrase "born to the purple" to mean "of noble birth." In order to preserve this color that displayed nobility, the jealous and suspicious Roman rulers even announced such a cruel decree: "Any person outside the court who wears a purple robe shall be punished with death." This pigment rendered immortal service in establishing the ancient trading centers of Phoenicia.
In ancient times, even colors carried certain superstitious and religious overtones. The ancient Greeks used colors to represent what they believed were 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 afterward spread to England, used colors as specific emblems: golden yellow represented honor, red represented courage, and blue represented loyalty and filial piety. Today in Western universities, robes with shoulder capes of different colors still represent a person's particular academic status. The emperors of ancient China 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 a fever-reducing effect on patients with high fever, a purple environment can comfort pregnant women, 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 more quickly. 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 even earlier, he proposed the idea of making synthetic dyes, when natural alizarin and indigo still dominated the market. These pigments required large amounts of natural plants to produce and could no longer satisfy the needs of industrial development at that time. Only 18 years old, Perkin tried to synthesize quinine in a small shed in his backyard. When he mixed aniline sulfate with dichromate, he obtained a red-purple product - mauveine. In fact, this dye is a group of compounds with similar structures. From then on, synthetic dyes developed rapidly, among which the most important were picric acid, magenta, and rosolic acid. Today, synthetic dyes have become an important chemical product widely used in textiles, papermaking, soaps and detergents, and the plastics industry. Color makes the world around us gorgeous and colorful, and makes our lives rich and varied. When 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 brilliant color, making our work efficiency higher,
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 for releasing fry, a salmon 35 decimeters long and weighing 0.5 kilograms was actually found. These fish usually live in the cold waters deep in the Pacific Ocean. Astonishingly, the only connection between this fish pen and the outside waters was a maze-like outlet pipe, with a 75-centimeter-high fence and wire mesh in between. People simply could not imagine how this unyielding "warrior" had endured all hardships and crossed all obstacles to arrive here. To commend its glorious feat, people erected a 5-ton mahogany statue by 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 streams and the plants growing by the water on the banks are also different, thus making the smell of each stream different. These smells pass through the fish's nostrils and leave a strong mark 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 endure hardship to return to their hometown.
The catfish is a blind creature with a keen 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 any 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 with one another.
Like fish, insects, reptiles, and even higher mammals rely mainly on smell among the many pieces of information around them, and sometimes odors are also used by animals as a means of communication. Thus, for many animals, smell is the key to their lives.
Among reptiles there is a blind snake that can track ants by the scent they leave and go to the ant nest to hunt ants. At the same time, it also secretes a scented substance itself. This scent has several functions: to deal with worker ants that may attack it; to warn other insect-eating snakes that this ant nest now belongs to me, so do not come to compete for food; and it can also rely on this scent to find its own companions.
The sense of smell of mammals is also very sensitive. Many animals rely on scent to find food, or use smell to detect enemy animals and escape in time. Especially those herbivorous animals generally do not have very good eyesight. Therefore, in finding food and guarding against enemies, they rely even more on their keen sense of smell. Some mammals, like the blind snake, leave special scents on bushes and grasses in their living areas as markers, which is equivalent to issuing a notice to animals of the same species: this place has been occupied. Thus fights over territory are avoided. These scents are usually emitted by animal urine or animal endocrine glands. For example, antelope deer, musk deer, and others have this kind of special secretory gland.
A dog's sense of smell is astonishingly acute. According to research, a shepherd dog's nasal cavity contains 22 million olfactory cells, covering an area of 120 cm2, while a human's 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 scent left by the criminal to track him for several kilometers or even dozens of kilometers and catch him.
Insects, these lower animals, depend even more strongly on chemical information for survival. For example, when some insects are threatened or attacked by outsiders, 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 distinguished by other ants.
The role of insect sex pheromones is even more magical. For example, the queen bee secretes a sex pheromone: 9-keto-alpha-nonenoic acid (also called 9-oxo-2-decenoic acid). Its odor can prevent ordinary worker bees from developing into queens. The termite king in a termite colony can also secrete some similar substances that hinder worker ants from developing into kings. The sexual behavior of insects is even more deeply influenced by sex pheromones. The sensitivity of male moths to the sex pheromone of female moths is astonishing: it can detect a female moth 2 kilometers away. Such high sensitivity is beyond the reach of all kinds of human analytical instruments.
For the highest form of life - 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 as low as 1-10-7 ppm (one part per million is 1 ppm). Such trace amounts of substances are something the eye, which "detects the minutest detail," simply cannot see. Therefore, although many trace substances cannot be seen or touched, we can rely on smell to discover their existence. Some hunting peoples, such as the San people of South Africa and the Australian Aborigines, still use their keen sense of smell to find and track wild animals.
Human body secretions also contain various chemical substances that can trigger the sense of smell in animals or humans. The main odor in human sweat is butyric acid (CH3-CH2-CH2-COOH). If 1% of the butyric acid in sweat seeps into the sole of a shoe, then each footprint can leave at least 2×1011 molecules of butyric acid. These molecules are 100 times the minimum threshold of human smell, so people should originally be able to smell them; it is only because habituation lowers the efficiency of smell for this butyric acid that 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 is also different. A dog with a keen sense of smell can distinguish each person's different scent 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 smelling odors associated with them. For example: distinguishing the fragrance of apples is a characteristic of diabetic ketoacidosis patients; a person whose body emits the yeasty smell of freshly baked black bread indicates typhoid fever; patients with schizophrenia often emit a strong human body fragrance during the critical period of 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 "spiky" 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 that 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 receptors are basically compatible with the shape and volume of gas molecules, that is, only when a gas molecule of a certain geometric shape fits the special shape of a receptor can it cause smell. It is just like a stopper that can only tightly fit a bottle of one caliber. According to this theory, each receptor must correspond to one primary odor, which is obviously impossible. Therefore, although this theory can explain many phenomena, it is still doubted 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 chemistry experiments can smell the odor of a certain substance even if there is only 10-14 grams of the gas, which is far below the detection limit of laboratory instruments.
It is now 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 receptors. Some also propose that these substances must also be soluble in lipids, so that they can pass through the lipid cell membranes of the receptors. 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 - the banana scent of n-butyl acetate (CH3COOC4H9), the pear scent of isoamyl acetate (CH3COOC5-H11); the pineapple scent of methyl butyrate (CH3H7COOCH3); the orange scent of n-octyl acetate (CH3COOC8H17); the apple scent of isoamyl isovalerate (C4H9COOC5H11), and so on - all possess 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 the odor also affects the odor; for example, skatole at high concentration is a nauseating stench, but when extremely dilute it becomes a pleasant smell.
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 having evolved from the olfactory organ of the primitive brain. Therefore, odors can actually sometimes also trigger certain memories.
In land animals, the difference between taste and smell is very great. Odors diffuse in the air, while tastes exist in solution. For aquatic animals the difference is not great, because chemical stimulants are all dissolved in solution.
Applications of Smell
Humans began producing various products to stimulate the sense of smell long ago. Although living things evolved to the advanced stage of humans, with language, thought no longer needs to rely on smell for transmission. But several thousand years ago in ancient China, the incense people burned and the fragrances sprinkled on clothes were probably the earliest aromatic substances produced by humans to stimulate the sense of smell. Perfumes were also widely used in Greece and ancient Rome. In the Bible, the wise men often carried gold, frankincense (baldanum), and myrrh; the latter two are gums used as spices. Only when the Crusaders brought spices back to Europe from the Arab world did Europe first learn to make spices.
With the development of production, people's demand for spices increased exponentially. After synthetic spices were put into production at the end of the 19th century, the output and variety of spices continuously increased. At first, spices were processed from flowers or other parts of plants to obtain essential oils. The processing methods could use steam distillation, or extraction with volatile solvents such as benzene and ether and with fats and oils, 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 only about one ton of roses. The main components of essential oils are terpenes. Turpentine contains a large amount of terpenes, so turpentine is a major raw material for spice production. For example, the geraniol in it has a rose fragrance. Some spices are also obtained from the secretory glands of certain animals, such as castoreum from the Canadian beaver, civetone from the American civet, and muscone from the musk deer. Ambergris is a waxy high-grade spice secreted by whales (sperm whales). Perfume is usually made by mixing essential oils, animal spices, and chemical additives in alcohol. It should be pointed out that the chemical properties of the mixed perfume must be stable, but also must not be too stable. Moreover, for ordinary people, the odor and the acidity and alkalinity to the skin must both be moderate. Highly skilled experts with keen smell can blend various spices into intoxicating high-quality essences. These experts rely entirely on their many years of practical experience and extraordinary sense of smell when blending spices. Therefore, people with dull smell cannot undertake this work.
Besides perfume, a large number of commodities are also treated with spices 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 less obvious fragrances. Even in dishwashing water, hand soap, household cleaners, and detergents, people often add the fragrance of pine or lemon.
There are also some foul odors in nature. The filthy smell of rotting meat and the odor given off by excrement are mainly due to compounds such as putrescine (H2N-(CH2)4-NH2, 1,4-diaminobutane), cadaverine (H2N-(CH2)5-NH2, 1,5-diaminopentane), and skatole. These substances are the products of the decomposition of amino acids that make up proteins. These extremely foul odors are also useful. They can help us identify spoiled and deteriorated 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 foul odors. So how can we resist these odors and prevent them from stimulating our olfactory organs? One method is to use surface adsorbents or chemical reactions to remove the molecules of the foul odor; another method is to use a stronger fragrance to mask the unpleasant odor; and a third method is to weaken or anesthetize the olfactory nerve endings, in which case although the odor still exists, it will not cause a response in the olfactory nerves. In recent years, the most important area in the research and application of smell should probably be 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
have an effect on insects. The amount of sex pheromone contained in the bodies of insects is very, very small, so separating them out and clarifying their structure and properties is an extremely difficult task. But considering the huge economic losses caused by the damage insects bring to crops and other agricultural products, and the economic benefits that artificially controlling the behavior of some beneficial insects may bring to humanity, scientists overcame all kinds of difficulties to engage in research on sex pheromones. In 1959, humans for the first time isolated and identified an insect sex pheromone - the silkworm moth sex attractant. This work was obtained by a group of German workers who spent several years cutting off the abdominal tips of more than 500,000 unmated female moths. The pure sex pheromone product obtained this time was still 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 already 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, which are then killed with drugs. A higher concentration of attractant can also be released to confuse male moths, preventing them from mating, so that these pests are left without offspring. Because this kind of insecticide uses very little medication, is very economical, and does not cause environmental pollution, it has attracted increasingly widespread attention.
Through in-depth study of these sex pheromones, it was found that insects use sex pheromones with very high specificity. The so-called specificity is what we often call "one key opens one lock": each sex pheromone acts only on a certain behavior of a certain insect, so that confusion in nature can be reduced. Bombykol is released by female moths to attract male moths; heptanone is released by ants to warn their companions. People have already studied using it to repel mosquitoes and ants from disturbing humans and livestock. The sex pheromone molecules used by insects for warning are generally relatively small, so that they can volatilize quickly, take effect rapidly, and do not need high species specificity. Therefore, some drugs that repel mosquitoes and flies can also drive away ants.
We have only taken the first step in the study of smell, or rather, we have only mastered 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 beautiful, people must frequently wash clothes, bedding, and daily tableware and tea sets. Therefore, soap and various detergents have formed an indissoluble bond with us.
The invention of soap was much earlier than that of detergents. It is said that more than three thousand years ago, on Mount Sapo outside Rome, it was accidentally made by people. On this sacred mountain, when people burned offerings, the fats and oils dripped down onto the wood ash and became the most primitive soap, and these soaps seeped into the surrounding clay. People discovered that when they sat on this clay and their clothes were stained with the clay, the clothes actually became easier to wash clean than before. People began to regard it as sacred soil, and only later realized that this was an unintentional harvest of human labor.
In 70 AD, the Roman scholar Pliny described the process of making soap with goat fat and wood ash. In this process another thing had to be added - sea salt. It can 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 the output at that time was very low, it could only be used by rich people; it was a luxury item for the filthy. In 1791 the French chemist Nicolas Leblanc used electrolysis of an aqueous sodium chloride solution to produce sodium hydroxide. The reaction equation is:
2NaCl + 2H2O ?electrolysis? 2NaOH + H2↑(gas) + Cl2↑(gas),
From then on, soap became something that ordinary people could all use. However, not everyone knew what soap was. From 1811 to 1823, after M. E. Chevreul studied soap products, he satisfactorily explained what soap is and the chemical reactions in making soap. As scientists clarified the principle of soap's detergency, various synthetic detergents came into being.
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 do not have detersive or cleaning effects. Because the salt of triethanolamine 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 contains triglycerides, and the hydrolysate of wood ash contains potassium hydroxide or sodium hydroxide. When they are heated together, the fat is 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 surface of the liquid. This process is called salting out in industry. It can then 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 then air-dried until only 10%-15% water remains, when it can be cut into pieces. With further drying until the water content is
only 5%-10%, 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 detersive ability, it must contain a long chain of more than 9 carbons, and the detersive ability increases with the number of carbons.
The chain grows stronger. However, soaps containing more than 18 carbon atoms 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 lies between the ninth and tenth carbon atoms, that is, right in the middle of the molecule.
Therefore, soap containing 18 carbon atoms has good washing power, while soap whose molecules contain 12 carbon atoms has enhanced solubility in water. Soaps made of long-chain molecules containing more than 18 carbon atoms are used only as scouring fillers. Such scouring agents need detersive power without needing solubility.
Since the principle by which soap removes dirt became understood, people have tried to improve its performance. For soap has quite a few drawbacks. For example, it dissolves poorly in cold water and only dissolves well in hot water; in acidic solutions it cannot do a good washing job, because in acidic solutions it decomposes into insoluble acid soap and lumps of fatty acid. In addition, soap reacts with calcium, magnesium, aluminum, iron and other elements in water (forming so-called metal soaps). This is why basins and buckets that have held soapy water show ring-shaped scum, and why fabrics washed with soap show a faint film. Soap is an excellent 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 the washing performance of soap, chemists first had to understand the principle by which soap removes dirt. The process of removing dirt is to remove grime and grease with a very thin film - this film carries the dirt into solution, where it is removed by emulsification or in suspension. In addition, a detergent must be able to lower the surface tension of the water interface, so that the washing liquid can penetrate into the tiny crevices of fabrics, thereby speeding up the wetting of the fabric.
In fact, most organic detergents are made as dipole molecules, the molecule being a long chain of 12 to 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 detergent remove dirt?
The principle of detergency
For a substance to have detersive power, it must first be able to lower the surface tension of the solution. The surface tension of pure water is 272 dynes per cm. But to be an effective detergent it must lower the surface tension to 230 dynes per cm, and only a very small amount of detergent is enough to lower the surface tension to this value.
A typical force acting on a water molecule can cause a molecule at the water surface to enter the solution -
- and this creates surface tension. When soap molecules are added to water, they float to the surface, because the organic end (hydrophobic) is repelled by the polar water molecules. Because the soap molecules at the water surface are repelled by water molecules, a force is produced that opposes the mutual attraction of the 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 fiber. At the same
time, the water keeps writhing underneath, speeding up the departure of the oil droplets. The polar groups in cotton fibers (such as the hydroxyl group -OH in cellulose) can attract water, causing the water to spread (penetrate) throughout the fabric. Overall, the reactions of removing dirt and grime are broadly similar. However, because the dirt may be electrically neutral,
or positively charged or negatively charged. Therefore, some modification of this simple theory is 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 suffered a shortage of fats during World War I, scientists were prompted to research new detergents.
Fritz Gunter invented 1,4-diisopropylnaphthalene-6-sulfonic acid and sodium dibutylnaphthalenesulfonate. Although neither is an ideal detergent, 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 a larger area of soiled fabric than soap, and it also did not leave a film that interfered with dyeing. Moreover, it also dissolves in cold water, and neither hard solutions nor hard water affect it.
Since then, with the development of the synthetic fiber industry and the growing 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; perfumes; and some also contain a small amount of enzymes.
Synthetic detergents The molecular structure of synthetic detergents is similar to that of soap, both containing 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 commercially available detergents are anionic detergents. Cationic detergents are for industrial use, for example, 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 wants less foam, and too much foam affects the rotation of the pulsator and reduces cleaning power. Adding 2-octanol silicone or 2-ethylhexane silicone to anionic detergents can also achieve the purpose of reducing foam.
Builders (boosters) They are used to complex those ions that make water hard (mainly calcium and magnesium ions, as well as iron, aluminum and other ions), so that they enter the solution, thereby making the dirt suspend in the solution and preventing it from settling out. At the same time, builders can give the washing water a suitable alkalinity, thereby helping to dissolve acidic dirt. The most commonly used builders are phosphates, but sometimes carbonates, silicates or
borates are 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 class.
Emulsifiers Their role is to prevent dirt particles from redepositing on the fabric and to keep the dirt suspended in the water so it floats 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. Thus they neither aggregate to form precipitates nor readily cling to the fabric.
Bleaching agents When the dyes in clothes are exposed to sunlight, oxygen and air pollutants, their chemical structure changes, leading to fading or darkening of the clothing. 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 dyes 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
of impermeable film, thereby protecting this part of the metal from corrosion. If it is added to detergent, it can prevent corrosion of metal parts such as washing machines, metal buttons and zippers. Sodium silicate not only has an anti-corrosion effect, it is also a 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 a detergent absorbs moisture and cakes during storage, its dosage will increase when used. This is not only because caked detergent is not easy to dissolve completely, but also because it readily settles 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. Thus, after a cationic agent is added, it tends to combine with the fabric fibers. The softener also has a long organic chain-like “tail”, which acts like a lubricant and gives people a soft feel. Softeners also have an emulsifying effect and can retain moisture, thereby reducing the accumulation of static charge on the fabric surface. Therefore, the feel performance is improved.
Colorants and perfumes If soap and detergent were all made white, consumers would inevitably find it dull. If we add a small amount of pigment to make these detergents light blue or pink, consumers will feel more comfortable. In addition, soap and detergent undergo slow chemical reactions during storage, producing unpleasant odors. To counteract these odors, some perfumes must be added. Enzymes A few years ago, enzyme-containing detergents began to appear on the domestic market. When using such detergents, we often have to soak the clothes in warm water. 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 action 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 breaking down 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 it has good washing power, it has returned to the market and is deeply welcomed by consumers.
Foaming agents Foam can make suspended oil or dirt float on the water surface and be rinsed away. Generally speaking, lowering the surface tension increases foam, and nonionic detergents foam rather poorly. There is a class of nonionic compounds that do not foam; they produce foam for only a very short time. When a solution containing such a detergent
flows into a ditch, 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 power. This view is correct for soap, but it is 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 rinsing water. If the detergent contains sodium chlorophosphate, formed 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 consumption of soap and synthetic detergents has increased day by day. In the United States, the average person consumes as much as 28 pounds of soap and detergent per year. In our country in recent years, in addition to everyday washing powder, various new types of 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-used anionic synthetic detergent, especially sodium alkylbenzenesulfonate (ABS), has this pollution
problem. Because the hydrocarbon group in its molecule is branched, it is very difficult for bacteria to decompose (also called degrade). Therefore, in the sewage of sewage treatment plants the concentration of this detergent is often very high.
In 1965 the U.S. government announced: 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, what is commonly used is linear alkylbenzene sulfonate (LAS). 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 lethal danger. Fortunately, in general wastewater treatment plants its concentration is rarely higher than a few ppm; this concentration can kill those troublesome intestinal bacteria and can also reduce the sludge residue in sewers, thus cleaning the pipes and keeping the water flowing freely.
In addition, the builders contained in detergents, sodium tripolyphosphate and sodium pyrophosphate, are very good chemical fertilizers; they 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 frenzied growth of aquatic plants can block river channels and lake branches, seriously affecting water traffic. In addition, when large numbers of aquatic plants die, they consume the oxygen in the water and also release toxic gases such as methane and hydrogen sulfide, poisoning the water quality and making it impossible for fish and other aquatic animals to survive. According to statistics from Britain, the United States and other countries, 30% to 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 types of detergents are constantly 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 problem of water pollution caused by washing water, and take preventive measures before trouble occurs.
Hazardous chemical substances
Lead pollution and its prevention and control
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, under the circumstances of foreign invasion and internal turmoil, rapidly moved toward destruction. In recent years, research into why the once illustrious ancient Roman Empire declined so quickly 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: 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 with lead either. Although they could not enjoy high-grade lead vessels and did not need cosmetics, do not forget that ancient Rome once had the most advanced water supply and drainage system of ancient mankind, and at that time the water pipes carrying drinking water 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, which 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 present-day humanity. 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 authorities conducted a survey of 102 residences in the above areas. When they tested 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 the standard, a blood lead concentration of 100 micrograms per liter is already severe lead poisoning!
So where did the lead poison in these children's blood come from? People found that the houses they lived in were all more than forty or fifty years old, long unrepaired, assailed by damp, and the paint on the walls had long since loosened and peeled off. Tragically, these children often dug off paint fragments with their fingernails and chewed them in their mouths, 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 bit of 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 stage of development and are more susceptible to damage; at this time it often leads to lifelong ailments, such as epilepsy, poor intellectual development and muscle paralysis. In addition, because the metabolism of lead 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 “fishes 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 lead tetroxide 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 in the manufacture of paint.
However, at present the lead pollution with the broadest harmful impact on 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 brought in a compound called tetraethyl lead to help: adding less than 1 gram of tetraethyl lead per liter of gasoline is enough to prevent the fuel from premature detonation. Tetraethyl lead is toxic, so people add some pigments 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 the gasoline itself
cannot burn, so it 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 it had achieved lead-free gasoline; the United States began producing unleaded gasoline in 1975, and by 1988 achieved lead-free 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 issued regulations in 1991 on the use of unleaded gasoline in automobiles. By 1994, 99% of the countries in the world had prohibited the use of leaded gasoline.
However, due to various reasons, our country is still using leaded gasoline now, but has already been actively preparing for the use of unleaded gasoline: in 1991, China's petroleum department issued the national-level standard for “unleaded motor gasoline”; in 1992, at Shuangyushu in Haidian District, Beijing, China's first unleaded gasoline filling station with a green sign appeared; subsequently, senior officials of China's Ministry of Transport let it be known to the public: China strives to achieve lead-free gasoline by 1996??
Indoor environmental pollution
After his defeat at Waterloo, the outstanding hero of his generation, Napoleon, was imprisoned on St. Helena in the South Atlantic,
and died suddenly of an acute illness in 1821. Some pathologists verified that he died of arsenic poisoning, because his attending physician had the record that “in the last 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 his heart beat violently before he died.” These symptoms are completely similar to the symptoms of arsenic poisoning.
By the 1960s, unexpected 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 making a plaster mold, that is, first shaving off the hair, applying plaster paste to the face to obtain a negative mold, and then turning it into a face mask. At that time, a personal bodyguard, for permanent remembrance, devoutly kept 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 hides the secrets of the entire human body. Each hair contains about more than 20,000 cells and contains various chemical elements. Because the concentration of the contained elements is high, the sensitivity and accuracy of testing exceed those of blood and urine tests. Therefore, in recent years, the simple and accurate “hair diagnostics” has developed rapidly.
The British scientist Smith used neutron activation analysis technology to analyze several strands of Napoleon's hair and 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 wall of Napoleon's room on St. Helena was pasted with green wallpaper. The green pigment composition at that time contained arsenic compounds. Under normal circumstances, this arsenic compound is still relatively stable and would not harm people. But in the humid environment of St. 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 to die of 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 silk banner 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 plastic-sprayed wall surfaces made her feel the warmth of modern life. However, one month later she felt dizzy and weak, and soon a large number of bleeding spots appeared on her skin. Blood tests showed that her hemoglobin, platelets and white blood cells were all reduced, and she was diagnosed with “aplastic anemia.” She sought treatment in many places with little effect, and later 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 found the cause in time and prescribed the right medicine, so that she recovered her health.
The doctors of that department believe that what made this female worker suffer from a blood disease was precisely those painted furniture and plastic-sprayed wall surfaces that had once given her warmth. So-called plastic spraying is actually a novel multi-colored 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 themselves non-toxic; the problem is that some solvents and other additives are quite toxic. After being applied to furniture and walls, the solvents and additives slowly volatilize and will harm people's health. For example, the solvent xylene in plastic spraying and the solvent benzene in paint are both toxic. If a person lives in a room that has not long been decorated, 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 odors 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 household pollutant.
Now, in order to eliminate pests such as mosquitoes, flies, bedbugs and cockroaches, many families keep insecticides. Recently, spray insecticides are more commonly used, mostly in cans with nozzles; when using them, one only needs to press the nozzle lightly and an aerosol can be sprayed out, 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 belong to this class. This type of insecticide is highly toxic to insects but less toxic to humans, though 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 often also has a certain toxicity. The low-boiling aerosol carriers loaded into the can, 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 degree of indoor air pollution 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 astonished 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 and chemistry experts to inspect the dormitory.
The dormitory manager was called over, and upon asking, it was learned that this dormitory building had already been in use for many years. This dormitory was located on the ground floor, right next to the toilet. Because the toilet's sewer had leaked for a long time, the dormitory's cement floor and the wall next to the toilet had been made stained and stinking. 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 exactly entered the school a year and a half earlier and had lived in this newly repaired dormitory as soon as they enrolled. The experts chiseled off some bricks and cement to take back for testing, and finally the truth came out: the building materials used in the repairs contained radioactive substances, which release radon gas and cause malignant pathological changes in the human body. The university students became ill precisely because they were murdered by this invisible “killer,” radon.
Experts are no strangers to 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, the British scientist Rutherford and his collaborator Owens were studying the radioactivity of thorium compounds. Once, Owens happened to open 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, repeated similar situations made them notice that even a slight air flow would cause a large part 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 found 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, the British scientist Ramsay determined that these emanations were themselves a new element, and like some inert gases already discovered, it was an inert gas. Thus, a new member was added to the periodic table of elements - element No. 88, radon.
Radon is a product of the decay of radioactive elements such as uranium and radium. 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 one element in nature 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 in radon's decay accumulate on the walls of human bronchi and lung 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 sixty-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 good health, took to her bed, and finally Old Zhao also fell ill. Some superstitious people thought this was a “haunted house,” but Old Zhao's burning incense and worshipping 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, and only then was the mystery of the “haunted house” solved.
Some people believe that our country's current level of science popularization is relatively low; if one investigates carefully, perhaps many baffling deaths and disease incidents can all 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 part 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 its 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 the 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, part of it rises toward the surface through cracks in the rock strata and seeps into the soil. It can enter indoors from the foundation interlayer or floor gaps of a house, and can also enter indoors through underground pipes. Because there is no 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 currently received by humans, 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. The story of its origin must begin with World War I.
In the spring of 1915, on the western 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, a pig was also on the scene. At first, the poison gas made it unbearably suffocated, so it desperately rooted at the soil with its snout and then buried its big mouth in the loose 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 loose soil played the role of 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, also based on the principle that sodium carbonate and sodium thiosulfate can react with chlorine gas:
Na2S2O3+4Cl2+5H2O Na2SO4+H2SO4+8HCl
they developed a cotton cloth anti-gas mask soaked in solutions of these two substances. But the effect was not ideal: first, the cotton cloth mask had little adsorptivity; 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 both have considerable adsorptive effects on various poison gases.
Thus, Zelinsky concluded: there is absolutely no need to find defensive items for each kind of poison gas, because the molecules on the solid surface have an adsorptive effect on any kind of poison gas. As long as one chooses a substance with a larger solid surface than cotton or soil, that is, a substance with a greater ability to adsorb gases, it can deal 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 strength to make it play a role. Zelinsky's experiments proved that charcoal itself can not only adsorb gases, but because it has a porous structure, it can also let fresh air pass through unimpeded.
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 let only oxygen and
other harmless gases pass through. Activated carbon is made by dry distillation of wood, hard nut shells (such as walnut shells) or animal bones. Dry distillation is heat treatment under conditions isolated from air. Through dry distillation, the cellulose and lignin in the wood all become 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 also be treated under high-temperature steam at 800 to 900°C to remove these blockages. The activated carbon made in this way has the characteristics of being light, loose and porous. Each gram has a surface area of several hundred square meters. Because its ability to adsorb gases is especially strong, its anti-poison effect is even better
.
With the assistance of a Russian engineer, Zelinsky also successfully designed a gas mask. This was a short thick canister mounted in front of a face mask, positioned exactly 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, it stood the test of practice and received affirmation and praise. It once saved the lives of tens of thousands of soldiers in World War II. No wonder people wanted to hang 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 caused by eating too much or catching cold, doctors often have you take some medicinal charcoal (activated carbon). Medicinal charcoal can adsorb miscellaneous matter in the intestines, reduce the stimulation of this miscellaneous matter on the intestinal mucosa, and play a role in relieving pain and stopping diarrhea. In sugar factories, activated carbon is also an important player. However, here 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 dazzlingly white refined sugar containing more than 99.7% sucrose - high-grade white sugar. It is also worth mentioning that when a spacecraft travels in outer space, it must have a separate ecological system, in which the air is recycled after supplementing an appropriate amount of oxygen. The gas exhaled by astronauts must first have 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 recycled. The chemical substance loaded 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 life
Food The color, aroma and taste of food
The colors of foods are mostly artificial coloring, with edible pigments added during production. Some foods' colors are due to their own content of certain natural pigments. For example, the green color presented by the stems and leaves of green vegetables and unripe fruits is chlorophyll; the red color of tomatoes is tomato pigment; the shells of shrimp and crabs contain crustacyanin, which can appear red after being heated.
The aroma of food comes from volatile substances such as alcohols, aldehydes, ketones and esters. Fish, meat and eggs all contain rich proteins. Protein itself has no umami taste, but after cooking it is hydrolyzed into various amino acids, and amino acids have a delicious taste. Among amino acids, glutamic acid has the most delicious taste. “MSG” is the sodium salt of glutamic acid. When sucrose is diluted with water to 200 times, sweetness can no longer be felt, while when MSG is diluted with water to 3,000 times, its umami taste can still be tasted! Recently, a strong MSG made by mixing sodium glutamate with sodium inosinate has also been developed, and its umami taste is 40 times that of MSG. The bodies of shrimp, crabs, snails and clams contain a lot of succinic acid, so they have a unique umami taste loved by people. The aroma of cinnamon is due to its content of cinnamaldehyde, while the aroma of liquor comes from fusel alcohols and esters produced during fermentation. The aroma of bananas is the volatilized isoamyl acetate, and the aroma of citrus fruits comes from their content of nerol. As for the aroma of pastries and candies, it is due to the addition of artificial fruit flavor essences.
In our country, people are accustomed to dividing tastes into the “five flavors” of sour, sweet, bitter, spicy and salty. Sourness is caused by the 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 cabbage contains lactic acid; the sour taste in fruits, beverages or candies comes from their components citric acid, tartaric acid, malic acid and vitamin
C and so on. Sweetness is caused by sugar substances such as sucrose, fructose, glucose, maltose and lactose. When making cakes
When it comes to pastries, biscuits, popsicles and ice cream, an appropriate amount of saccharin is 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 a person's appetite.
Most substances containing alkaloids have a bitter taste, such as coptis chinensis and cocoa. Tea leaves contain 5% caffeine alkaloid, and the stronger the tea, the more bitter its taste.
Chili peppers contain capsaicin, scallions and garlic contain allicin, ginger contains gingerol, the pungency of mustard and radish comes from mustard oil, and pepper contains piperine.
Everyone knows that table salt is salty. When a compound contains both a monovalent cation and the anion of a monovalent acid, it has a salty taste. Examples include the chlorides, bromides and iodides of potassium and sodium. For kidney disease patients who cannot eat salt, sodium malate, which also produces a salty taste, can be used as a substitute.
Besides these "five flavors," there is one more taste, which is astringency. Some fruits such as persimmons and plums have an astringent taste because they contain tannic acid.
In short, taste is the different sensations caused by the chemical-physical stimulation of substances contained in food acting on the taste nerves.
Food colorants and flavorings Food colorants are dyes used to color food and beverages, and are generally organic compounds. There are two types of food colorants: one is natural colorants, which are extracted directly from animal and plant bodies.
For example, yellow carotene can be extracted from carrots. A purplish-red colorant called amaranth red can be obtained from red amaranth. Red colorant is extracted from the body and secretions of cochineal insects. The other type is artificially synthesized colorants made by chemical methods, most of which are synthesized using coal tar as a raw material.
Generally speaking, natural colorants have more advantages than synthetic ones. Many natural colorants have certain nutritional and medical value. For example, turmeric is extracted from the roots and stems of the traditional Chinese medicine turmeric, and has the effects of promoting blood circulation, dispersing blood stasis, soothing the liver and relieving depression. Carotene can be converted into vitamin A in the body. However, extracting natural colorants from animal and plant bodies is very difficult, and the yield is not high. Moreover, natural colorants have poor stability, cannot withstand high temperatures, and are afraid of encountering acids and alkalis, so their color easily changes and fades. Synthetic colorants, on the other hand, overcome the above shortcomings, with stable properties, convenient use and low cost, but most artificially synthesized colorants are aromatic compounds with very large molecules, which generally cannot be digested by people and have no nutritional value, only serving to enhance color and give people a feeling of beauty.
Adding flavorings to food can give food a pleasant aroma and enhance people's appetite. Food flavorings can also be divided by source into two major categories: natural food flavorings and synthetic food flavorings. Natural
food flavorings are mainly extracted from natural fruits, such as coffee, cocoa, almonds, oranges, pineapple, bayberry, etc. This kind of natural flavoring can be directly added to fruit juice, soda, canned food, and its aroma is the same as natural fruit fragrance, which is endearing.
However, due to the influence of source and quantity, natural flavorings are already far from meeting the 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 artificially imitated and synthesized. However, the aromas of various foods are each different, and the components are also quite complex. For example, as many as 81 aroma components have been identified in apples. The flavor components in watermelon aroma 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 technique is also a combination of art and science. Food flavoring technicians can blend many kinds of natural flavorings, synthetic flavorings, and appropriate blenders and auxiliary agents into various food flavorings with many varieties and realistic aromas.
Food colorants and food flavorings enter the human body along with food, so the issue of their being hygienic and non-toxic is very important.
The consumption of "monosodium glutamate" "Monosodium glutamate" tastes very delicious, and when stir-frying 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 too much? "Monosodium glutamate" is also called "wei su," and its chemical name is sodium glutamate. It is a white crystal, often
made from gluten or soybeans as raw materials through chemical processing. Gluten and soybeans are both foods rich in protein. People put them into dilute hydrochloric acid and boil them for several hours to hydrolyze the contained protein into various amino acids, then evaporate and concentrate the solution under low pressure, add calcium carbonate and an appropriate amount of lime to remove excess hydrochloric acid, then add alcohol. At this point, glutamic acid precipitates out in the form of a double salt of calcium glutamate and calcium chloride. Separate the precipitate, dissolve it in water, then add sodium carbonate, evaporate and concentrate, and white sodium glutamate crystals are obtained
- monosodium glutamate. Sodium glutamate can be hydrolyzed into glutamic acid, and glutamic acid is one of the amino acids, which has a strong savory
taste. According to experiments, after monosodium glutamate is diluted 3000 times with water, it still has a savory taste. Glutamic acid is a main component of human protein, so monosodium glutamate has relatively high nutritional value. Adding a little monosodium glutamate when stir-frying dishes or making soup will make the soup and dishes more delicious, thus increasing appetite and inducing 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 to 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. Because sodium glutamate combines with excess ammonia in the blood to form glutamine, it can make the symptoms of patients with hepatic coma improve rapidly, 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 cooking methods. When cooking, do not add monosodium glutamate too early. If cooking and heating reach above 120°C, sodium glutamate will undergo a chemical change and become pyroglutamate sodium, which not only reduces the savory taste but also has slight toxicity. Therefore, when stir-frying 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 with added alkali or baking soda, so as to avoid the sodium glutamate in monosodium glutamate becoming disodium glutamate and losing its savory 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 high blood sugar. In addition, the more monosodium glutamate the better is not true either. When stir-frying dishes or making soup, adding an appropriate amount of monosodium glutamate is enough to enhance freshness. Adding too much monosodium glutamate will instead make the tongue feel 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 it is also an indispensable nutrient for maintaining normal human life. Eating sugar can replenish the energy consumed by the human body. Sugar is very easily absorbed by the human body. According to analytical testing, after eating sugar
for 3 minutes, the blood sugar content in the blood can increase. 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 saving protein. When 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 conducive to the synthesis of protein in tissues.
Although white sugar has high nutritional value, scientific sugar consumption cannot be ignored.
The best times to eat sugar (1) Before bathing: bathing causes heavy sweating and consumes physical strength, requiring replenishment of
water and energy, and eating sugar can prevent fainting. (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 nauseous: eating some sugar can raise blood sugar, stabilize mood, and help restore normality. (5) When vomiting and having diarrhea: due to 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 remaining in the oral cavity is conducive to bacterial reproduction, forming acidic substances, corroding the enamel on the surface of the teeth, and forming dental caries. (3) After eating one's fill: eating sugar again at this time will make people fat and promote diabetes. (4) For those with dental disease: eating sugar will induce toothache and aggravate 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 developing cancer. Calcium deficiency in the elderly can cause osteoporosis and make bones fragile and easily broken; calcium deficiency in children makes them prone to rickets.
Eating too much sugar also has the following harms:
(1) It is easily converted into fat and stored, making one 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 large amounts of sugar for a long time 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. In addition, table salt is an important industrial raw material and can be used to manufacture soda ash, caustic soda, hydrochloric acid, polyvinyl chloride plastics, etc. 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 of seeds, 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 causing them to die.
In daily life, table salt also has many uses. If you can use it cleverly, it will bring you much convenience. For example, adding a little salt when washing clothes makes the clothes less likely to fade. Adding a little salt when dyeing clothes can make the color bright and firm. When deep-frying food, add a little salt to the pot, especially when frying fish; sprinkling a little salt on the fish meat can prevent hot oil from splattering. 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 clean the stomach and intestines and make bowel movements smooth. Regularly rinsing the mouth 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 decocting it for drinking can stop vomiting and diarrhea; if hot water has reddened the skin, wiping a little table salt on it can reduce pain.
Table salt is a friend of people's lives. Washing hair with salt water can avoid hair loss. Newly bought porcelain or glassware, if first boiled in salt water, is less likely to break; putting a knife in salt water to soak for half an hour makes grinding easier and makes it easier to grind it sharp; eggs with broken shells, if boiled in salt water, will not leak out the egg white; tea stains on tea sets can be removed by wiping with a cloth dipped in table salt; when growing flowers in a vase, adding a little table salt to the water can keep the flowers fresh for a longer time; adding a little table salt to paste can prevent spoilage and increase the viscosity of the paste; wiping furniture with table salt can make the furniture smooth and bright. The reserves of table salt in nature are extremely rich. The vast sea is the main place where table salt resides. If all the table salt in seawater were extracted and spread on 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. At this rate of production, table salt could be used by 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, salty is the most basic. If it is missing from meals, soup and dishes, they will be bland and tasteless. More importantly, the human body cannot maintain normal physiological functions without table salt.
Human blood contains about 0.6%-0.9% table salt. Under such conditions, the heart can beat normally and muscles can maintain stimulus responsiveness. When the human body loses a large amount of water, it will simultaneously be accompanied by a large loss of table salt. Doctors often treat this by subcutaneous or intravenous infusion of physiological saline (0.9% sodium chloride aqueous solution). Table salt is often excreted with sweat during human metabolism. Workers engaged in high-temperature operations, or after intense physical labor or strenuous physical exercise, should pay attention to drinking some salt boiled water to replenish the content of table salt in the body. 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 "hyponatremia 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 acid-base imbalance. 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 persistently eating 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 cause 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 a little, but it should not be too much either. 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 myocardial work, are used to replace sodium. There are two formulas: one is salt for general consumption, 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 drinking tea
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 subjecting them to processes such as fixation, 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 leaves through processes such as withering, rolling, fermentation and drying. The tea leaves
are called black tea because the chlorophyll becomes red-black under oxidation by oxidase. Oolong tea is a semi-fermented product, and its nature lies between black and green tea. The jasmine tea commonly drunk in ordinary life is made by scenting green tea with fragrant and rich jasmine flowers.
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 is tea polyphenols, accounting for about 20%-30% of dry 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, mainly caffeine (tea essence), which has the effect 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, etc. These vitamins are all nutrients needed by the human body, and they have preventive effects on some 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. Therefore, 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, with about 75-100 milligrams of fluorine per kilogram of dry tea. Therefore, regularly drinking tea can take in enough fluorine to meet the human body's demand for fluorine, which is beneficial for protecting dental health and preventing dental caries.
Tea can also neutralize acid poisoning caused by eating too much protein or fat due to a partial diet. People in pastoral areas often eat meat and drink milk, and they 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 to the human body caused by radioactive substances.
If tea leaves are brewed for too long or left overnight, especially in summer, they very easily deteriorate and turn sour. Drinking them again is harmful to human health.
Drinking hot tea is more beneficial than drinking cold tea. Hot tea entering the stomach can soften food, strengthen stomach wall contraction, promote gastric juice secretion, 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 high 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 fragrance and taste of tea.
People love drinking tea and are also very particular about tea sets. The material of tea sets has a certain
influence on the taste quality of tea. Practice has proved that for brewing tea, finely made pottery tea sets are best. Because pottery has certain tiny pores and a certain air permeability, with moderate heat conduction and heat preservation suitable for extracting the effective components of tea leaves, the brewed tea is very good in color, aroma and taste. The aromatic oils of tea leaves will volatilize when subjected to high heat, so tea leaves should not be brewed with boiling water, let alone 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, magnolia tea, etc., precisely by using this characteristic of theirs of easily absorbing other odors. Also because tea leaves have this characteristic, they easily take on other flavors and cannot be stored together with other things.
However, drinking tea too much or in inappropriate amounts can also bring many adverse consequences. The theophylline and tannic acid in tea leaves irritate the gastrointestinal tract. Drinking strong tea in large amounts, especially on an empty stomach, can cause stomach discomfort and stomach pain, and induce and aggravate gastric or duodenal ulcers. The tannic acid in tea leaves has an astringent effect and easily causes constipation. Because tannic acid can form insoluble iron tannate with iron in the intestinal tract, affecting iron absorption, drinking too much tea can cause anemia. Caffeine and theophylline can speed up the heartbeat, and drinking large amounts of tea poses a risk of inducing and aggravating 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 use grains, potatoes and sweet potatoes rich in starch
as raw materials to make alcohol through fermentation. 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 ?malt?ose enzyme?
55-60 ℃
2C 6 H12 O 6
Maltose glucose Alcoholization stage:
C 6 H 12 O 6
Alcoholizing 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 medicine"
used to make glutinous rice wine contains strains such as amylase, maltase and alcoholizing enzyme. When making glutinous rice wine, first steam glutinous rice (or good-quality rice) until half cooked, let it cool, then add wine medicine powder and mix well,
and ferment at a temperature of 25-30°C. The amylase, maltase and alcoholizing enzyme then multiply in large numbers, promoting the generation 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 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 while others do not. Beer is made using 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 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 several kinds of alcohol is not high, that is, they contain relatively little ethanol, so acetic acid bacteria in the air that get into the alcohol cannot be killed by the alcohol, and they reproduce and cause trouble inside, oxidizing ethanol into acetic acid.
C 2 H 5OH + O 2 ?????? CH 3COOH + H 2 O
White liquor, however, contains a lot of ethanol, so as soon as acetic acid bacteria get in, they are killed, and therefore white liquor does not easily turn sour. As the saying goes, the older the alcohol, the more fragrant it is. Because in addition to 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-term 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 esters Therefore, the longer alcohol is stored, the richer and more fragrant its mellow aroma. For the world-famous Moutai, 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 drink to their heart's content. Is drinking alcohol beneficial or not? On this, people have different opinions and mixed praise and blame. Those who like to drink
praise it extremely, giving it the fine names "nectar" and "jade liquid," while those who dislike alcohol say it is good for nothing, even denouncing 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 alcohol is beneficial or not; what matters is to pay attention to scientific drinking.
Beer has very high nutritional value and has the fine name of "liquid bread"; yellow wine contains 17 kinds of amino acids, and drinking some yellow wine is also good for health; wine contains vitamin B1, B2 and C, and also contains vitamin B12, which treats pernicious anemia; white liquor has a relatively high alcohol content and a relatively strong toxic effect on people, and its nutritional
value is also not as good as that of beer, yellow wine and wine, but it also contains components beneficial to the human body, and it is often used to make medicinal alcohol and tonic alcohol. 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 of harming health. Whether it is alcohol itself or its metabolite acetaldehyde, both are harmful and not beneficial to the human body. To prevent alcohol from harming people, pay attention 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 cries abnormally, feels dizzy, vomits, sleeps unconscious, 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 being greedily unwilling to put down the cup. The practice of showing off in front of others, egging people on, forcing others to drink more, or showing off one's "sea capacity" is not advisable.
(2) Do not drink on an empty stomach. 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 and causes harm to the body's organs. Therefore, when drinking, 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 less alcohol content and relatively more nutrients, such as beer, yellow wine and wine. If drinking white liquor, choose low-degree white liquor of excellent quality with no strange taste, no mixed taste and not too strong irritation.
(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 poet Li Bai of the Tang Dynasty left exquisite verses that will be remembered for all ages, but because he was addicted to alcohol, he ended up dying after "entering the water to grasp the moon after drinking."
Some people are also accustomed to drinking a few cups before going to sleep, seeking the muddled state 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 alcohol, people know to abstain from drinking early, but they do not know that drinking at night is even worse. Once drunk and full, one sleeps and goes to the pillow. The heat congesting harms the heart and eyes. The night qi is restrained, and alcohol causes it to be released, disturbing one's clarity, overworking the spleen and stomach, causing dampness to stagnate and sores to form, stirring fire and increasing desire, and thus many people become ill because of it."
By the way, people who are obese are even less suitable for regularly drinking alcohol. Because white liquor and beer are both made from grain, and fruit wine also contains relatively more sugar, 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 quite a lot of meat and dishes, and salt intake also increases markedly, thus causing an excess of nutrition and calories in the body and leading to obesity.
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 becoming even 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 activities 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, etc.
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 maturity will be inhibited, and brain development will also
be affected, and smell and taste will also become abnormal. For example, some children like to eat cinders and soil, and even eat them with relish, while they are averse to eating fish, meat, etc. 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, mussels, etc. 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. More than 99% exists in bones and teeth in the form of apatite, and the remaining calcium is mainly distributed in body fluids. Calcium in the blood is mainly distributed in plasma, and the calcium content in plasma is related to phosphorus concentration and protein concentration. In plasma, the normal product of calcium and phosphorus is 40, that is, the milligrams of calcium and inorganic phosphorus per 100 milliliters of plasma multiplied together equals 40. When it is less than 30, one may have rickets, and then it is necessary to supplement it from food. Calcium ions have the function of inhibiting neuromuscular excitability. In plasma, calcium per 100 milliliters is 8.5-11.5 milligrams. 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% exists 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 human body weight respectively. They exist in the human body completely in ionic form, 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 pH
value of body fluids constant, ensuring the environment necessary for normal physiological functions.
Copper Copper accounts for about 0.00015% of human 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 iron absorption. Copper can also promote iron to enter the bone marrow from storage sites and accelerate the synthesis of hemoglobin. When the body lacks copper, iron supplementation treatment is of no help. 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 copper basins can prevent and treat eye diseases.
Chromium Chromium is an element we are very familiar with. Bicycle handlebars, wheel rims, and steel pipes of tables and chairs are often plated with a layer of chromium on the surface to prevent steel from rusting and to be bright and beautiful. Chromium is also a trace element necessary for our human body, and there is more in childhood and less in adulthood. If the human body lacks chromium, it will cause atherosclerosis. Ordinary fruit juice, coarse grains, fish, lean meat and shellfish all contain relatively much 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,
pernicious anemia will result.
Iodine The human body contains about 20-50 milligrams of iodine, of which more than 40% exists in the thyroid gland near the throat. It is an important raw material for synthesizing thyroid hormones. Thyroid hormones can enhance the metabolic capacity of the human body and promote the body's utilization of sugar, protein and fat. When iodine intake is low, thyroid hormones cannot be secreted normally, and a person's neck will swell; this is suffering from the disease of goiter. It is generally believed that iodine deficiency in the environment
and the inability of the human body 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 components and effects 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 a bad odor. What is the reason for this? It is mainly because the temperature and humidity in the oral cavity are very suitable for bacterial reproduction, and food residue eaten gets stuck between the teeth and ferments and spoils. When food spoils, it also produces acid liquid that corrodes the teeth. Therefore, one must brush teeth and rinse the mouth promptly after eating to be hygienic and to make the mouth feel comfortable.
Brushing teeth must use toothpaste, because food remaining in the oral cavity can firmly attach to the surface of the teeth, and only with the help of the abrasives and detergents in toothpaste can the teeth be brushed clean and made bright and beautiful. Brushing teeth 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 components of toothpaste.
Toothpaste is composed of various inorganic and organic substances, including abrasives, washing and foaming agents, binders, humectants, sweeteners, aromatic agents and water. In recent years, various drugs have also been added to toothpaste to make 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 mouthfeel and sufficient foam.
The abrasive is the main body of toothpaste. Commonly used abrasives include calcium carbonate (CaCO3), calcium hydrogen phosphate
(CaHPO4·2H2O), with an amount of 30%-55%. In order to increase the decontamination effect, it is also necessary
to add the washing and foaming agent sodium lauryl sulfate (ROSO3Na), with an amount of about 2%-3%. Toothpaste can
The whitening of teeth mainly relies on the action of two ingredients. The abrasive has a certain friction, and the detergent foam agent has the effect of cleaning and producing foam. Combined together and with the action of the toothbrush, they can brush away the dirt on the surface of the teeth, making the teeth as white as jade.
Adding spices (such as mint, spearmint, etc.) to toothpaste not only gives a fresh and fragrant feeling during use, but also has a bactericidal effect, eliminating bacteria in the oral cavity and preventing the paste from spoiling. To make the toothpaste taste good, some saccharin is also 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 firm and white, the choice of toothpaste is generally considered from the 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 toothpaste containing phosphorus 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 and sodium fluoride; for teeth that feel numb and uncomfortable when exposed to cold, heat, sourness or sweetness, anti-acid desensitizing toothpaste can be used; for teeth that often swell, ache and bleed, Chinese herbal medicine toothpaste with anti-inflammatory and pain-relieving effects should be chosen. Medicated toothpaste not only has the effect of cleaning the oral cavity and teeth, but can also play a role in preventing and treating dental disease, so it is generally welcomed by consumers, and its output also ranks first. China is rich in Chinese herbal medicine resources and has a wide variety, using them to prepare medicated toothpaste gives mild medicinal properties and few side effects, which is a unique advantage.
Although toothpaste can clean the oral cavity, 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, clearing away food remaining in the gaps between the teeth, so as to prevent food residue at night
from spoiling in the oral cavity and producing odor and corroding the teeth, and to avoid the deposition of tartar, then it will be even more in line with hygiene requirements.
Fluorine and Teeth
In the human body, fluorine 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 physical health. After food is chewed up 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 the chewing process, a large amount of saliva will be secreted in the oral cavity, and under the action of salivary enzymes, the food is broken down 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 broken down. On the contrary, if one wolfs down food when eating, or cannot chew the food well because of bad teeth, the 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 to protect them or protect them improperly, resulting in a sharp increase in dental diseases, such as dental caries, which 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 broken down by bacteria in the oral cavity 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 decalcification of the inorganic substances in the hard tissues of the teeth, including tooth enamel, cementum, and dentin, and the decomposition of organic
substances. 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 self-repair ability, 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 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 tooth brushing, fluoride ions can also combine with calcium in the shallow layer of tooth enamel to form poorly soluble calcium fluoride, which has a strong inhibitory effect on Lactobacillus and a certain preventive and therapeutic effect on dental caries. When using these medicated toothpastes, if the toothpaste can remain in the oral cavity for a longer time, the effect is even better. But after use, be sure to rinse away the residual toothpaste in the oral cavity.
In recent years, many medical prevention experts in China have proposed preventing dental caries by drinking tea. This is because tea leaves have a strong enrichment effect on fluorine in the environment and have a relatively high fluorine content. The people of China have a traditional habit of drinking tea. It has the effects of cutting grease, refreshing the mind, and nourishing the body. Tea leaves contain amino acids and proteins needed by the human body as well as inorganic trace elements, but in terms of their fluorine content, they can both “treat disease” and “cause disease.” Drinking tea in moderation can prevent dental disease caused by fluorine deficiency in the body, and is also of great benefit to adolescents and children.
Daily Life The Chemical Knowledge of Boiling Water
Boiling water is a small matter in daily life, but little do people know that there is also quite a bit 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 for bubbles appearing when boiling water. When the bottom of the kettle is heated, some water molecules gain energy and become vaporized molecules. As the temperature rises, there are more and more vaporized molecules, forming 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 changes from small to large, but when the water is boiled, the sound suddenly becomes smaller again. Why is this?
Experiments prove that when water is heated from normal 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 of the kettle body and the temperature of the water differ little, 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 in the kettle is also high, the movement speed of water molecules accelerates, while the convection speed is slow, and the temperature difference between the upper and lower layers of water in the kettle is about 3°C. Some water molecules gain relatively high energy from the bottom of the kettle, become vaporized molecules, form bubbles, escape from the water layer, strike the kettle body, and emit sound. When the water temperature reaches the boiling point, because of the tumbling of water bubbles, the temperature of the boiling water and all parts of the kettle body is equalized, and the sound suddenly becomes smaller. As the saying goes: “Water that makes noise is not boiling, boiling water makes no noise,” and this is the reason.
After the water is boiled, if it is poured onto the ground, because the rapid evaporation of water molecules creates an “air cushion” effect, it gives off 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 less soluble Mg(OH)2: MgCO3+H2OMg(OH)2+H2CO3
Expressed by one overall chemical equation: Mg(HCO3)2Mg(OH)2+2CO2
Calcium carbonate and magnesium hydroxide are deposited at the bottom of the kettle and adhere to the kettle wall, forming scale (commonly known as “water alkali”). Scale has very poor heat conductivity. If scale accumulates in a kettle, the water is not easy to boil. For every 1 millimeter increase in scale thickness, fuel consumption increases by 5%. If scale accumulates in large boilers, there is also the danger of causing an explosion. How can the 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 the hard scale become loose and very easy to remove. If scale accumulates in a thermos bottle, it affects the heat preservation effect. To remove the scale in the inner liner of a thermos bottle, hydrochloric acid, which is more acidic than acetic acid, can be used, with even better results.
CaCO3+2HCl=CaCl2+H2O+CO2↑
Mg（OH）2+2HCl=MgCl2+2H2O2
Talking About the “Gas Tank”
With the rapid development of China's petroleum industry, in cities, many families use a “gas tank.” A “gas tank” seems to be understandable from its name, that it contains 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 gas plant, it is transported to thousands of households through gas pipelines. Liquefied petroleum gas, however, is a by-product gas from oil extraction or oil refining, and its main components are propane, butane, propylene, and butylene. People make use of the easy liquefaction of these gases by 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 in terms of both source and composition, liquefied petroleum gas and coal gas are different. In this sense, 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 upon 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, so when it leaks, it is not easy to volatilize away, but spreads along the ground like water and may stagnate in low-lying places, very easily reaching the explosive concentration. If a person stays in a kitchen where liquefied gas is leaking, the combustible gas can not only adhere to clothing and skin, but may even be inhaled into the lungs. Once it encounters an open flame, the serious consequence of being burned inside and out can occur. Liquefied petroleum gas has a pungent special odor and is easy to detect. Once a leak is found, doors and windows should be opened in time for ventilation.
When using liquefied petroleum gas, the steel cylinder should be kept far from the fire source (generally more than 1 meter 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 bake it, which is extremely dangerous. Because baking will cause the vaporization speed to increase sharply, and the gas pressure inside the steel cylinder will rise sharply, creating the danger of causing the steel cylinder to explode. Also 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 is already 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 cover the steel cylinder guardrail with a towel, rag, or apron, 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 ?combustion??ignition? 3CO + 3H O
3 6 2 2 2
Propylene
C4H8+6O24CO2+4H2O Butylene
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, and at the same time 3 times the volume of propane in carbon dioxide is released. In the same way, the amount of air required and carbon dioxide released from burning 1 volume of butane, propylene, and butylene can be calculated separately. 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 and may even give off 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 meets 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, recorders, and color TVs are placed should be separated from the kitchen as much as possible. As for rice cookers, washing machines, and so on, after use, do not still leave them in the kitchen; wipe them dry and move them to another room. Color TVs, recorders, stereo systems, and so on, when not in use, should 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 the 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, a flickering blue flame can be seen. 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 the occurrence of 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%, only 10 minutes are needed to cause death. Carbon monoxide has no color and no odor and is not easy for people to detect. 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. With the north wind piercingly cold and the chill pressing in, closing
doors and windows is necessary, but one must be alert to this invisible and odorless gas launching a 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, pay even more attention to indoor ventilation, and leave ventilation openings on the windows. If a coal gas poisoning accident occurs, immediately put the patient in a ventilated place, taking care not to let them catch cold. In severe cases, send them to the hospital in time
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 not soluble in water and cannot undergo chemical changes with water. Water cannot play a role in absorbing carbon monoxide. Others say that if coal gas poisoning occurs, drinking a little vinegar or sauerkraut soup can detoxify it. This also makes no sense, because carbon monoxide cannot react with the acetic acid in vinegar or the lactic acid in sauerkraut, and cannot eliminate the toxic 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 under very high pressure can not only quickly relieve the patient's symptoms of oxygen deficiency, but also accelerate the dissociation of carbon monoxide from hemoglobin. According to measurements, at 1 atmosphere of pressure, the half-life of carboxyhemoglobin is 520 minutes, while at 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 cabin, so it is called a hyperbaric oxygen chamber. According to clinical observations, without treatment with a hyperbaric oxygen chamber, the mortality rate of coal gas poisoning is 11%-15%, while with treatment using a hyperbaric oxygen chamber, the mortality rate of severe coal gas poisoning is 4%-6%. It has been reported that using a hyperbaric oxygen chamber for treatment once
saved the life of a coal gas poisoning patient who had been unconscious 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 composition of black powder is “one saltpeter, two sulfur, three charcoal.” Yes, but you should know that the “one, two, three” here means that the first component of black powder is potassium nitrate, the second is sulfur, and the third is charcoal, but the mass ratio of these three components is not 1:2:3. In fact, black powder is prepared according to the following ratio: 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, producing a large amount of gas. Ignition
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 sky, where it gives off 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.), combustibles (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 firecrackers is ignited, these substances undergo a series of complex chemical changes, producing a large amount of gas and releasing 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. At the same time, they also irritate the mucous membranes of the human respiratory tract, damage lung tissue, and even induce respiratory diseases.
Physical Pollution Setting off a large number of firecrackers produces 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 for a single firecracker are: Flash Thunder 130 decibels, Big Green Whip 125 decibels, both exceeding the noise produced by a heavy anti-aircraft machine gun. These noises have a very strong stimulating effect on the human nervous and auditory systems. In addition, firecracker noise also has the characteristic of impulsive sound, that is, rapid onset and high peak value, so it can cause fright and deafness, aggravate the condition of patients with high blood pressure, 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 occur frequently.
After firecrackers explode, a large amount of torn 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 lamp 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 a “neon lamp.”
A neon lamp 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 that are at energy levels close to the nucleus are excited to higher energy levels farther away. However, 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 principle of neon lamp luminescence.
For different gas atoms, the atomic structure is different, and the energy released when electrons jump back to their original energy levels after excitation is also different. The frequency of the corresponding radiated electromagnetic waves is therefore different, so the colors of the glow we see are also 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 powder,
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 the condensation of water, but there is also a kind of ice unrelated to water, and that is: “dry ice.” Dry ice is formed by the condensation of 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 still, 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 the hands, because its temperature is as low as -78.5
°C, and it will freeze the 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 survey team members used a drilling machine to bore into the ground. When they drilled very deep, suddenly gas underground sprayed out from the borehole at a pressure of more than 900 kilograms, and immediately a large pile of white “snowflakes” accumulated at the mouth of the borehole. This was dry ice. The curious survey team members touched it with their hands, and as a result, their hands either blistered or turned black. Deep in the strata, some places gather a large amount of carbon dioxide, which under the enormous pressure of the earth's crust becomes liquid. When the drilling machine reaches that place, the high-pressure gas quickly 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 of 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 for rain.” Using an airplane to scatter dry ice into the sky, it suddenly vaporizes and takes a large amount of heat from the cloud layer, cooling the cloud layer to -40°C. After each kilogram of dry ice vaporizes, it can form 100 quadrillion tiny ice crystals in the cloud layer. When the surrounding cloud and mist encounter the small ice crystals, they condense on them and become large water droplets, which fall as raindrops. From the time the dry ice was scattered, in less than 20 minutes, a good rain fell. In a short while the rain passed and the sky cleared, and the thirsty crops, in the warm sunlight and the moist air, flourished again.
On the stage of movies, television, and drama, one can see fairies dancing gracefully in a paradise wreathed in clouds and mist, and the all-powerful Sun Wukong riding the 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 quickly vaporizes, absorbs heat, the air temperature suddenly drops, water vapor condenses, and a large amount of white mist forms. Then the wonderful scene of rolling white clouds and wreathing mist appears on the stage. In addition, using dry ice to present special scenes such as flying waterfalls and flowing springs among high mountains and steep ridges, or river embankments bursting and floods spreading, also has quite good effects.
A Panacea from the Soil - About Antibiotics
Antibiotics of all kinds are now commonly kept medicines in hospitals, pharmacies, and even homes. People use them to overcome various vicious pathogens that threaten human health. Not long ago, diseases such as bacterial pneumonia, meningitis, and pulmonary tuberculosis caused by rampant and arrogant pathogens such as streptococci and tubercle bacilli were still regarded by people as incurable diseases certain to end in death. Since the advent of antibiotics, the miracle of “recovery as soon as the medicine is taken” has appeared in those dying patients, and many patients have been saved from the brink of death. At first, they were “miracle drugs” more expensive than gold, but today they can be bought for just ten or twenty cents. They are not only widely used to kill bacteria 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 are not gifts from God? They are truly “native and locally grown” on Earth, and to find and produce them, people paid a very arduous price. Now new members are still constantly joining this family, becoming a newly emerging force in the pharmaceutical industry.
One
Like many other medicines, the use of antibiotics came much earlier than their discovery. That is to say, before people understood their true nature, 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 Qimin Yaoshu recorded the divine yeast for treating diarrhea and dysentery, and the red yeast mentioned in Tiangong Kaiwu more than 300 years ago were the earliest antibiotic medicines.
The discovery of antibiotics began with penicillin, and this is also 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 can inhibit bacteria, pointing out that it was precisely “life inhibiting life.” In 1889, a French chemist first used the word antibiotic to name such substances.
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 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 the British bacteriologist Alexander Fleming, while studying staphylococci, had his specimen accidentally contaminated by soil containing humus, thereby growing green mold. And wherever these green molds went, the staphylococci disappeared without a trace. Around the green mold appeared a blank circle, 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 vicious 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 was because the amount of penicillin contained in these filtrates was really too small. If a patient used this penicillin to treat a disease, at least tens of thousands of milliliters of filtrate would be needed, which would require as much culture medium as a small pond. Therefore, this experiment could only remain in test tubes.
Eleven years passed. When Howard Florey of Oxford University in England was looking for new drugs to treat bacterial diseases, he read Fleming's paper, which aroused great interest in him. He cooperated with the chemist Ernst Chain and began the arduous work of manufacturing penicillin. Chain racked his brains and improved the method of purifying penicillin, but after the improvement this work was still arduous and tedious. The entire 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. In the course of their research, 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 human bedpans, to culture the Penicillium.
After several months of effort, they produced only a small pinch of brownish-yellow penicillin powder. They chose a policeman who was already dying from a bacterial infection with sores at the corners of his mouth 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 human metabolism, penicillin disappeared very quickly in the body. In just one hour, all the penicillin that had not taken effect was excreted cleanly in the urine. At this point, Florey had to give the patient a continuous drip of penicillin while collecting every drop of urine the patient excreted 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, but unfortunately at this point the penicillin had been used up, and there was not even penicillin the size of a needle tip left. The pathogens that were about to disappear rapidly multiplied again in geometric progression, attacking the still very weak patient anew, and finally took 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 medium. After World War II broke out, thousands upon thousands of wounded soldiers were carried from the front lines to rear hospitals for treatment, and Florey and his companions also came to the United States 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 from 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 market in Peoria - strain No. 832. At the same time, corn flour and lactose replaced the previous nutrient medium of broth and glucose, increasing the yield tenfold. In early 1943, the penicillin produced was only enough to treat a dozen patients. But two years later, penicillin had become a drug that could be bought in ordinary pharmacies. In 1944, the American bacteriologist Waksman screened from tens of thousands of soil specimens a Streptomyces that could kill tubercle bacilli, and from it isolated and purified
streptomycin. Scientists also studied 3,400 kinds of soil samples before obtaining chlortetracycline. 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 mold has an inhibitory effect on certain bacteria and to screen out these molds is indeed meticulous and arduous work.
First, countless soil samples that can culture fungi and have bactericidal value must be systematically screened. Usually, a diluted soil suspension is poured into Petri dishes with nutrient medium. After several days of culture, all microorganisms multiply, and colonies of various colors appear in the culture dishes, which can then be identified and isolated one by one. Then, they are transferred to slanted agar for further culture.
How can one determine whether the mold you have obtained can secrete antibiotics that kill pathogens? This requires further culturing the mold obtained above. A small-mouthed container holding this mold is placed upside down in a large culture dish, and the dish contains culture liquid inoculated with pathogenic bacteria. At this time, the antibiotic multiplies in the small-mouthed container and seeps into the culture dish from the stopper. 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 gelatinous 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 isolate. In order to increase the contact surface with air, liquid agar is often placed at a slant, and after solidification it becomes slanted agar.
The next step is to test the molds with promising potential and determine the activity spectrum of their secretions - used to determine their disease-resistance effect on pathogens. These pathogens include bacteria, yeasts, rickettsiae, and some things called viruses that are actually not viruses. Antibiotics, as the name suggests, are mainly used to resist bacteria. Ordinary antibiotics are powerless against true viruses.
When we have clarified the activity spectrum of the cultured antibiotic, 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 indeed has a significant disease-resistance effect, it can be further isolated and purified. To be safe, its toxicity to humans and livestock must also be tested, because antibiotics often have side effects. Only then is it used in industrial production. To increase the yield of antibiotics in industrial production, two approaches can be adopted: first, changing the composition of the culture medium; second, using new high-yield varieties to replace the original low-yield strains. High-yield varieties can be taken from samples in nature, or obtained by exposing strains to ultraviolet light, X-rays, or chemical mutagens to cause
mutation.
Three
After screening out molds that have bactericidal ability and high yield, they can be used to produce antibiotics. At present, antibiotics are still mainly produced by fermentation. The entire production is carried out in several stages.
Take the production of chlortetracycline (chlorotetracycline) as an example. First, purification must be carried out, and viable spores are preserved in sterile soil. Then culture is carried out in test tubes, which contain agar rich in nutrients. Then the colonies obtained from this step of propagation are washed into flasks containing culture medium for expanded culture. 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 reproduction process. Sometimes, in order to add specific active groups to the antibiotic, some ingredients containing these chemical groups are also added to the flask. For example, in penicillin production, adding phenylacetic acid can introduce a phenyl group into the penicillin molecule, thereby producing penicillin G with higher activity.
The next step is to transfer the bacteria in the flask to a large bottle for further expanded culture. Then the strain in the large bottle is inoculated into a fermentation tank for production. The containers used in each step must be strictly sterilized, and the fermentation tank and the pipes within it must also be sterilized with high-temperature and high-pressure steam, so as to ensure the purity of the product.
The main production is still carried out in the fermentation tank. During the reaction process, the temperature and pH in the tank must be strictly controlled. Usually, the pH value is controlled by adding acid or alkali. There is a spiral cooler inside the tank, with cooling water flowing through the pipe to control the temperature in the tank and prevent the large amount of heat produced during fermentation from making the temperature in the tank too high and killing the mold. In order to make the temperature in 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 “suffocate” due to lack of air, sometimes an antifoaming agent such as sterile lard must 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.
Four
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 or 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 serious side effects, and these drugs are usually only used to treat infections that carry relatively high risk.
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, certain 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 of the body that comes into contact with antibiotics has the possibility of mutation, the larger the antibiotic dose, the greater the possibility of cell mutation. Therefore, when using antibiotics, one must absolutely avoid overdose.
Another side effect of antibiotics is that they can produce and develop 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
but resistance can sometimes be passed from one generation to the next, and sometimes resistance can also be transmitted among different species of bacteria. For example, an ordinary 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 have now become the most commonly used drugs in clinical treatment, with antibiotics appearing in about 15% to 20% of prescriptions. 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 prescriptions in which antibiotics are prescribed for preventive purposes are superfluous. One document pointed out that about
20% to 30% of cold patients had antibiotics prescribed for them by doctors, even though antibiotics are completely ineffective against the common cold.
In one journal issue, an article signed by C·T Quinn 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 precious time. In the United States, some doctors simply use the telephone to fob 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 the only specific effective treatment for the pathogen causing the patient's infection.
Simmons and Stolley said that the most dangerous thing is the emergence of drug-resistant bacteria. For Gram-negative bacteria, this will more markedly alter the ecological habits of such bacteria. The emergence of such resistant bacterial strains inevitably leads to the need for larger doses of antibiotics or broad-spectrum antibiotics to deal with them. Materials indicate that whenever hospitals increase the dosage of antibiotics to prevent surgical infection, it inevitably leads to an increase in the probability of Gram-positive bacterial infection. 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 conclusions should be drawn only after further research on 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 drew up a plan to collect information on antibiotic use and to educate doctors that antibiotics should be used in appropriate amounts.
Five
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 the Second World War, because at that time there was a shortage of fish and other animal protein feed, and plant protein had to be used instead of animal protein to raise 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 in animal protein, plant protein could never make poultry and livestock grow as
fast as when they were fed animal protein. Logically, animal protein must contain something that plant protein lacks. Now, it has been clarified that this mysterious thing in animal protein is an animal protein factor called APF.
Scientists at the United States Department of Agriculture discovered that APF exists in the livers of animals, and APF was also found in cow dung, chicken manure, and even chicken manure from chickens that had never been fed animal protein. However, Western chicken houses use wire netting, raising chickens on elevated screens, and do not let 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 team from Merck & Co. and a British research team isolated it using less-than-ideal methods. They isolated from
the liver the long-sought anti-pernicious anemia factor, namely B12. They wanted to find out 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 discovered that this vitamin is produced by several microorganisms,
including Streptomyces, which had already been used to produce streptomycin. Before long, they used Streptomyces fermentation to grow pure B12 suitable for human use, and less pure BB12 suitable for feeding animals.
Other manufacturers immediately sought the potential market for this vitamin and looked for their own new methods of synthesizing it. For example, Lederle Laboratories used the aureomycin-producing Streptomyces to
manufacture 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 only a few parts per million of body weight, are enough to promote animal growth. Later, pharmaceutical manufacturers found that antibiotics such as penicillin, oxytetracycline and bacitracin had the same effect.
Today, antibiotics have become indispensable animal feed additives and are added to animal feed.
In 1973, the United States alone sold 88.4 million dollars' worth of antibiotics used for 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 the Escherichia coli that normally inhabit the animal body. Another theory holds that antibiotics reduce the likelihood of animals becoming ill. The basis of 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 becoming ill, they grow faster and stronger.
Whichever mechanism it is, the result of using antibiotics is indisputable: it enables 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 of pigs generally not fed antibiotics to reach the same market weight, and the former grow 30% faster than the latter. The same effect is also seen when feeding chickens and calves. Here is a question worth raising: if antibiotics are continuously added to feed, will the result be the production of resistant bacteria that attack the bodies of 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 possible potential dangers.
Antibiotics are a widely used and continuously developing new class of drugs. As long as we use them cautiously, maximize their strengths and avoid their weaknesses, they will certainly play a tremendous role in the struggle 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" has been growing louder day by day. Indeed, many scholars have turned their attention to nature and to the natural. They hope that by clarifying natural phenomena and clarifying the behavior of animals and plants existing in the natural world, they can then apply the principles and laws within, in order to achieve the purpose of learning and imitation. This is like a fresh breeze 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 secretion that prevents 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 a 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 (viscid threads), and contracted footing 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 moreover does so agilely and skillfully. But people have never thought about this. In any case, vaguely saying that "the web can only catch prey" is inappropriate and also unconvincing. Because no matter what thing it is, as long as it walks where there is no adhesive, it will likewise not be caught.
You might say the spider's eyes are especially sharp, but that would be 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, with the help of the regularly constructed web it can correctly judge the direction of the web's vibrations when the prey struggles, so that it can walk 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 the web, there is no need to worry much. For example: on the island of Madagascar there is a kind of spider that can catch small birds. When a person is caught by this ingenious web, as long as they do not flail about, they can seize the opportunity to walk away.
Someone may also raise this question: to catch prey struggling violently in the web, would not the spider, taking a shortcut without turning, also be caught by the web with adhesive? There is no need to worry about this at all, because the spider has a clear head. The adhesive threads are not covered all over with adhesive; the
adhesive exists as small droplets. Although when the adhesive is first applied by the spider it is full and even, 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 kinds of adhesive tape sold on the market today are almost all surface adhesive tape coated with glue over the entire surface, and there is almost no tape with point-like glue like a spider web.
In addition, an unnecessary doubt may also arise, namely: if a spider is caught by another kind of adhesive, what will it do? 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 (there is also a saying that the oily substance is first secreted from the spider's mouthparts and then applied to the limbs), so that 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 the recipe for the agar jelly food prepared for silkworms, published in 1962 in the British journal Nature.
At a glance one can tell 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 silkworms only eat mulberry leaves." They wanted to use it to prove that as long as there are these several components extracted from mulberry leaves, silkworms can eat food prepared according to this recipe just as they eat mulberry leaves.
In 1959, someone proposed a hypothesis: silkworms eat mulberry leaves because the lure of the scent drives the silkworm to move forward, then a special substance stimulates chewing behavior, and finally under the synergistic action of several substances, continuous feeding occurs. This hypothesis has already been proven by the following experimental facts.
Take a mulberry leaf and soak it in ether to dissolve out the scent and color. After such treatment, silkworms no longer approach the mulberry leaf. But if the above ether extract is dropped on filter paper, the silkworms will move toward the filter paper, but will not chew it. However, the silkworms do chew the mulberry leaf residue remaining after ether extraction. Then the mulberry leaf residue is extracted with hot methanol, and the extract is added to agar jelly. At this time, although traces of massive 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 the agar jelly, the silkworms not only chew well and swallow well, but also excrete feces.
After this, further research was carried out to separate from the ether extract (ME), the hot methanol extract (Mw), and
the mulberry leaf residue remaining after extraction with these two solvents (R) various factors such as attractant factors, chewing factors, and swallowing factors.
Silkworms can eat agar jelly containing mulberry leaf powder very well. At this time each silkworm can excrete about 20 silkworm droppings in one night; likewise, silkworms can also eat agar jelly containing ME, Mw and R very well, and can likewise excrete about 20 silkworm droppings. On this basis, the following experimental plan was further proposed:
extract the various active ingredients in ME, Mw and R, and modify them appropriately.
What was separated from ME was citral - a terpenoid essential oil - and β-sitosterol; what was separated from Mw
was isoquercitrin - a flavonoid pigment - and inositol, as well as sucrose; finally what was separated from R was potassium hydrogen phosphate, silicon dioxide and cellulose. After doing this, the agar jelly food containing the various ingredients in the above recipe was prepared, and silkworms could eat this food just like 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 be considered clearly explained from this aspect alone. Because from the composition of the several basic foods that silkworms eat, it can be seen that none of them are ingredients unique to mulberry leaves, since other plant leaves also commonly contain these substances. Therefore, since we emphasize "only eat mulberry leaves," we must proceed from a different standpoint from the above and introduce a hypothesis of "whether feeding-inhibitory factors exist." That is, without considering whether plant leaves other than mulberry leaves contain substances that stimulate silkworm feeding, we 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 "the reason silkworms only eat mulberry leaves" is that the various ingredients in the above recipe present 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 is it 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. The silkworm senses smell through its antennae; if the antennae are cut off, it cannot sense nearby mulberry leaves. What senses taste is the maxillae near the mouthparts. According to reports: silkworms whose maxillae have been cut off can eat cherry blossom leaves.
Later, through electrophysiological research, it was found that on the silkworm's antennae there are cone-shaped sensilla that can sense smell. In addition, among the several sensilla on the maxillae, Ss-I contains a sugar receptor that senses sucrose and a receptor that senses inositol; in the Ss-II sensillum, there is a receptor extremely sensitive to bitter substances, which can be considered the 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 in the future more receptor cells will certainly be identified. These different sensilla of the silkworm can sense not only feeding-stimulant substances but also feeding-inhibitory substances. It is the result of the synergistic action of these sensations that constitutes the control mechanism of feeding behavior.
The Secret of Why Crabs and Shrimp Change Color When Heated
Hairy crabs, green crabs, soldier crabs, pine-leaf crabs, swimming crabs, prawns, shrimp, lobsters?? Countless kinds of crabs and shrimp, when heated or cooked, generally also have their shells turn red (though with differences in depth). 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 crystalline form 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 kinds of crustaceans also adorn themselves with astaxanthin. However, some small crustaceans mainly contain crustacyanin, and some crabs contain 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 the 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 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 an entirely 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 the environment. And this difference is because the pigments exist in pigment cells in the skin, also called chromatophores. Under external stimulation, these cells can exhibit different states of hormone secretion, thereby causing the cells to expand or contract, and this expansion or contraction will cause the body color to change. But 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 objects are often combined with specific proteins in a special way, that is, they exist in the form of pigment proteins. However, this combination cannot significantly change the absorption peak that appears in its spectrum. Therefore, the color of carotenoids in solution and the color of carotenoids combined with protein are not very different. In this case, the color likewise will not show obvious change due to heating. Even if some color change can be seen at this time, it is merely the change of 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, in most cases, can absorb light of longer wavelength than carotenoids combined with protein, and even in extreme
cases can appear blue-green.