Process for crosslinking hydrophilic colloids

A process for crosslinking hydrophilic colloids which contain amino, imino and/or hydroxyl groups, which comprises incorporating into the hydrophilic colloid as a crosslinking agent a compound of the formula ##STR28## wherein each of X and Y are a fluorine, chlorine or bromine atom or a hydroxy group, a lower alkoxy group or a radical of the formula ##STR29## wherein R.sub.1, R.sub.2 and R.sub.3 are each optionally substituted alkyl, alkenyl, alkinyl, cycloalkyl, aryl, aralkyl or together with the nitrogen atom to which they are bonded form a saturated or unsaturated ring which optionally contains yet other heteroatoms, and M is a cation and Z is an anion, one of which or neither may be required to balance the charge in the triazine ring system.