Calcium sulfate, CaSO4, is a common laboratory and industrial chemical and an often used material in the building trade. It occurs naturally in various forms, which differ in their crystal water content: gypsum (CaSO4·2H2O), the hemihydrate (CaSO4·0.5H2O) also known as plaster of Paris, and the anhydrite. Despite its name the anhydrite is not always entirely devoid of water, the water content ranges from 0.0 to 0.05 mol-percent.
The main sources of calcium sulfate are naturally occurring minerals (gypsum and anhydrite). World production of natural gypsum is about 100 million tones per annum. Besides the natural sources, calcium sulfate is also produced as a by-product, mainly from the desulfurization of exhaust gases of fossil-fuel power stations.
Contributors and Attributions
- Hans Lohninger (Epina eBook Team)