Z 1305 (OTTO) Zinc sulphate, monohydrate, 99% Cas no 7446-19-7 - used in electrolytes for zinc plating. Z 1305 (OTTO) Zinc sulphate, monohydrate, 99% Cas no 7446-19-7 - used as an electrolyte for zinc electroplating, as a mordant in dyeing, and as a preservative for skins and leather.