Treatment of colored colloid layers

Claim 1

PROCESS FOR DECOLORIZING A WATER-PERMEABLE COLLOID LAYER CONTAINING A WATER-INSOLUBLE DYE COMPLEX FORMED BETWEEN A DYE AND AN UNCOLOURED SALT SELECTED FROM THE GROUP CONSISTING OF (A) ANION-ACTIVE ALKALI METAL, AMMONIUM AND AMINE SALTS OF LONG CHAINE SULPONIC AND SULPHURIC ACIDS WHICH CONTAIN AN ALKYL RADICAL OF AT LEAST 8 CARBON ATOMS IN THE ANION, AND (B) CATION-ACTIVE ALKYL SUBSTITUTED AMMONIUM SALTS AND QUATERNARY SALTS OF HETEROCYCLIC NITROGEN COMPOUNDS EACH OF WHICH CONTAINS A LONG CHAIN ALKYL RADICAL OF AT LEAST 8 CARBON ATOMS IN THE CATION, A BASIC DYE BEING SELECTED WHEN THE UNCOLOURED SALT IN ANION-ACTIVE AND AN ACID DYE BEING SELECTED WHEN THE UNCOLOURED SALT IS CATION-ACTIVE, WHICH COMPRISES TREATING THE LAYER WITH AN AQUEOUS SOLUTION OF AN UNCOLOURED SALT FROM GROUP (A) WHEN THAT PRESENT IN THE DYE COMPLEX IS FROM GROUP (B), AND FROM GROUP (B) WHEN THAT PRESENT IN THE DYE COMPLEX IS FROM GROUP (A), AND THEREAFTER WASHING THE LAYER WITH WATER.