METHOD OF PREPARING CHROME TANNER Russian patent published in 1999 - IPC

FIELD: leather industry. SUBSTANCE: invention concerns basic chromium(III) sulfate used as mineral tanner in leather and fur industries. Sodium or potassium bichromate is dissolved in sulfuric acid, after which chromium(VI) is reduced and desired product dried. To achieve reduction of Cr(VI), first 50% of Cr(VI) present in reaction mixture is reduced with sodium thiosulfate. 30% Cr(VI) is reduced with formalin or sulfur dioxide. Remaining 20% Cr(VI) are reduced with sulfur dioxide or formalin. EFFECT: increased quality of tanner. 2 ex