Chitosan solubility, biodegradability, reactivity, and adsorption
of many substrates depend on the amount of protonated
amino groups in the polymeric chain and thereby on
the proportion of acetylated and nonacetylated glucosamine
units. The amino groups (pKa from 6.2 to 7.0) are completely
protonated in acids with pKa smaller than 6.2 making chitosan
soluble. Chitosan is insoluble in water, organic solvents,
and aqueous bases and it is soluble after stirring in acids such
as acetic, nitric, hydrochloric, perchloric, and phosphoric