Simple Preparation of Chitin and Its Application in Orchid Growing

The application of chitin in orchid cultivation has already been reported, and some orchid enthusiasts may also be trying it. Many years ago, I prepared chitin because I was making absorbable surgical sutures and sewage flocculants. This year I watered my orchids with its solution again, and after several months I have found no negative effects; instead, there are some benefits, which is why I dare to write this out. I would not presume to say it is offered for the enjoyment of fellow orchid growers, but I must be prepared to take some criticism! (Winter is coming, and with nothing to do, I will make a bit of chitin to keep my hands busy. Also, in winter one does not sweat while doing it, so there is less suffering.) 1. Preparation of Chitin 1.1 Raw Materials Discarded shrimp, crab, and mantis shrimp shells, hydrochloric acid, sodium hydroxide, white vinegar 1.2 Vessels and Other Items A large beaker or large enamel jar, a deep stainless steel pot, a stove, a stainless steel wire skimmer, pH test paper (1-14) 1.3 Preparation Steps and Process Conditions Boil the shells in a 3% sodium hydroxide solution in a stainless steel pot for half an hour; the residual meat on the shells undergoes hydrolysis with the sodium hydroxide. Remove them and wash until neutral. Put them into a large beaker or large enamel jar, pour in a previously prepared 2-3% hydrochloric acid solution; at this point, a large amount of bubbles immediately forms, which is carbon dioxide. This reaction is: hydrogen chloride (hydrochloric acid) reacts with the calcium carbonate in the shells to produce carbon dioxide, calcium chloride, and water. Judging the endpoint of the reaction: when the pH is around 5 and it has soaked for a full day and night with almost no bubbles being produced. If the reaction ends in the middle of the night and you do not see it, it does not matter; add a little hydrochloric acid. If there are no bubbles, it can be regarded as the end of the reaction; if there are bubbles, continue soaking until the endpoint. Remove them and wash until neutral. Put them into a stainless steel pot, add a previously prepared 50% sodium hydroxide solution (note: add water first, then add sodium hydroxide, and never let the solution splash into your eyes, onto your skin, or onto your clothes), and boil for about ten hours. Take a small piece, wash it until neutral, put it into a small half-bowl of white vinegar diluted by half, and if it dissolves completely in about ten minutes, this can be regarded as the endpoint of the reaction. If it does not dissolve, or does not dissolve sufficiently, then boil it again until the reaction is finished. This reaction is the deacetylation of chitin by sodium hydroxide. Remove them, wash and soak multiple times until neutral, and dry for later use. (If the shells are first made into small pieces of 1-2 mm for deacetylation, the reaction time can be shortened.) Use white vinegar diluted two times to prepare a 5-10% deacetylated chitin solution for later use. 2. Application in Orchid Cultivation You may refer to the concentration used by orchid enthusiasts in Taiwan, China. Before use, add water to adjust the pH to about 6, or use it at a concentration of 0.2-1%. For its advantages, please refer to what orchid enthusiasts in Taiwan, China have said. (Liu Liming)