The principal use of salt cake in the pulp and paper industry is in the manufacture of sulfate pulp. Salt cake is an anhydrous sodium sulfate which contains varying amounts of impurities. The principal impurities usually are sulfuric acid, common salt, and sulfates of Fe, Al, Ca, and Mg. "Chrome salt cake," obtained as a by-product in making chromic acid, has a yellow color and contains Na2Cr2O7 (and/or Na2CrO4).
A complete analysis of salt cake is somewhat complicated and involves a considerable number of determinations, as outlined below. Since some mills are mainly interested in the acidity and the Na SO content, 2 4 directions for a "short analysis" are also given.
