Process for hardening gelatin

摘要

A process for hardening gelatin, which comprises incorporating in a gelatin-containing material at least one hardening compound represented by formula (I) <IMAGE> wherein R1 represents a substituted or unsubstituted aryl group, Z represents non-metallic atoms necessary for the formation of a nitrogen-containing heteroaromatic ring which may optionally be substituted, X(-) represents an anion, and n represents 0 or 1 provided that when n represents 0, the compound forms an inner salt. The gelatin hardeners can rapidly harden gelatin with little or no post-hardening and react with reactive groups of gelatin with high selectivity.