PRODUCTION OF CHROMIUM TRIOXIDE

摘要

Chromium trioxide is made by reacting sodium dichromate with sulphuric acid in an aqueous reaction mixture, evaporating the resultant liquor to cause crystallization of most of the chromium trioxide and to cause the concentration of sodium sulphates to be close to but below that at which sulphate crystals start to form, and separating the chromium trioxide crystals from the evaporated liquor. The liquor may then be cooled so as to cause crystallization of sodium sulphates, generally as sodium bisulphate, and the resultant liquor, after separation of the crystals, may be recycled to the reaction mixture containing dichromate and sulphuric acid.