A method of analysis has been developed that gives consistent results for soluble sulfate and total soluble salts in ceramic raw materials and bodies. Values for sulfate on a dry-weight basis ranged from 0.01 to 0.28% with ball clays, from 0.002 to 0.015% with china clays, and from 0.000 to 0.007% with miscellaneous raw materials. Bentonites were relatively high in sulfate, a Wyoming bentonite showing the highest value, 0.194%. The distribution of sulfate in the slip, cake, and press water was determined for eighteen ceramic bodies. An increase in the water-clay ratio in slips was found to increase the recoverable soluble sulfate (percentage dry basis). In experiments on repeated cycles of cake to slip to filter pressing, soluble sulfate continued to be released, but the bulk of the sulfate was obtained in the first pressing. Quantitative results are given on the effectiveness of barium carbonate as a precipitating reagent for sulfate in slips. Aging from six months to one year was found to have little effect on the soluble sulfate in stored samples of slips, cakes, and press waters. Dry storage, however, doubled the soluble sulfate content of a freshly mined ball clay within six months, evidently by oxidation of sulfur compounds.