Definition of water-soluble chitosan

Chitosan can only be dissolved in some dilute inorganic or organic acids, but not directly soluble in water, which greatly limits its application.
What is water-soluble chitosan? Conceptually confused, Do not know how to define ?
At least the following can be pointed out:
1 chitosan soluble in water;
2 Chitosan hydrochloride soluble in water;
3 carboxymethyl chitosan soluble in water;
4 low molecular chitin soluble in water;
5 low molecular chitosan soluble in water.
These are regarded by some people as water-soluble chitosan, in fact, only the first kind is the real water-soluble chitosan, it can be dissolved in water, and is the general chitosan, that is, neither chitosan hydrochloride, nor carboxymethyl chitosan, not low molecular matter.

How to judge if it is water-soluble chitosan?
It is easy to judge water-soluble chitosan, as long as it is dissolved in water.
First of all, see whether the solution is viscous, the non-viscous is low-molecular chitin or chitosan;
Secondly, adding a few drops of NaOH solution to this aqueous solution produces turbidity or precipitation, which is chitosan hydrochloride, because the hydrochloric acid in it is neutralized by alkali, chitosan is not soluble in neutral or alkaline water;
If a few drops of HCl solution are added to produce turbidity, it is carboxymethyl chitosan, because carboxymethyl chitosan is actually the sodium salt of carboxymethyl chitosan. If the solution is acidified, it is no longer the sodium carboxylate salt, but a carboxylate acid, which is insoluble in acidic water.