Water-Soluble Polysaccharide Neutral Salt Preparation

The patent uses acetic acid as an intermediary solvent to solubilize chitin and chitosan during derivatization reactions. The acetic acid enables the reactions to proceed while minimizing direct exposure to strong acids that would cause hydrolysis. After reaction, the product is precipitated and the acetic acid is removed, achieving both solubility improvement and hydrolysis prevention.

The patent changes the purification approach by adjusting physical parameters - specifically using precipitation from organic solvents and filtration based on particle size and solubility differences. This alternative purification method achieves separation without requiring dialysis membranes or gel permeation chromatography, thereby avoiding introduction of membrane fragments, endotoxins, or other contaminants associated with conventional methods.

The patent segments the purification process into simple, sequential steps: precipitation from organic solvent, filtration, and washing. Each step targets specific contaminants and can be performed rapidly. This segmented approach replaces the continuous, time-consuming processes of dialysis and gel permeation chromatography, reducing total purification time while maintaining high purity through targeted removal of specific impurities at each stage.

The patent converts the potential harm of using strong acids and complex purification methods into benefit by deliberately choosing acetic acid as the reaction medium and simple precipitation as the purification method. This approach initially seems limiting but actually produces cleaner products with fewer contaminants, thereby improving medical acceptability while maintaining application versatility. The 'harmful' constraint of using milder reagents becomes a benefit for pharmaceutical applications.