The Columbia Encyclopedia, Sixth Edition. Columbia Encyclopedia World Factbook American Heritage Coll. Most metal sulfates are readily soluble in water, but calcium and mercuric sulfates are only slightly soluble, while barium, lead, strontium, and mercurous sulfates are insoluble. Sulfates are widely distributed in nature.
Alums are double sulfates, containing two different metals and two sulfate radicals.
Organic sulfates are esters. They can be formed by reacting an alcohol with cold sulfuric acid. The Columbia Encyclopedia, Sixth Edition.