Process for the preparation of a chrome tanning agent and Glauber{3 s salt

摘要

A process for the preparation of a chrome-tanning agent and Glauber's salt from sodium bisulphate contaminated with chromium compounds obtained as by-product from the manufacture of chromic acid from solid sodium dichromate and sulphuric acid, comprising (A) TREATING AN ABOUT 20 TO 70% AQUEOUS SODIUM BISULPHATE SOLUTION WHICH CONTAINS CHROMIUM COMPOUNDS AND IS ACID WITH SULPHURIC ACID WITH SULPHUR DIOXIDE UNTIL ALL THE CHROMIUM IS PRESENT IN THE FORM OF CHROMIUM (III); (b) adding sodium hydroxide to the reduced solution until it has a pH of between about 4 and 5; (C) ADDING SODIUM CARBONATE TO THE SOLUTION TO A PH of between approximately 8 and 8.5, thereby precipitating chromium (III) hydroxide; (D) SEPARATING OFF THE PRECIPITATED CHROMIUM (III) hydroxide; and (E) EVAPORATING THE FILTRATE LEFT AFTER REMOVAL OF THE CHROMIUM (III) hydroxide to yield solid sodium sulphate.