Chitin is an important component of the arthropoda. The shell of arthropoda is washed by acid and base to remove calcium and protein

then unsolvable chitin is remained. The remainder is washed by concentrated base to remove acetyl

so the chitosan is available. Chitosan is more useful than unsolvable chitin . For getting a best method of chitosan preperation

the author did many experiments and obtained a few rules on theory and practice. They are valuable in studying chitin extraction and application.