Calcium sulfate, anhydrous

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White, odorless crystals whose mineral form is called Anhydrite. Anhydrous calcium sulfate is ground to form a colorless, inert pigment which is often used as a paper filler. It is strongly hygroscopic and is also used as a drying agent for solids, organic liquids, and gases. Anhydrous calcium sulfate is commercially sold under the name of Drierite®. Its drying capacity can be regenerated an unlimited number of times.

Synonyms and Related Terms

anhydrite; karstenite; muriacite; anhydrous sulfate of lime; anhydrous gypsum; Drierite



Chemical structure

Calcium sulfate, anhydrous.jpg


  • IntegraChem: SDS

Physical and Chemical Properties

Slightly soluble in water.

Composition CaSO4
CAS 7778-18-9
Mohs Hardness 3.0 - 3.5
Melting Point 1450 C
Density 2.93-2.964 g/ml
Molecular Weight mol. wt. = 136.14
Refractive Index 1.570; 1.614; 1.575

Resources and Citations

  • Richard S. Lewis, Hawley's Condensed Chemical Dictionary, Van Nostrand Reinhold, New York, 10th ed., 1993
  • The Merck Index, Martha Windholz (ed.), Merck Research Labs, Rahway NJ, 10th edition, 1983
  • R. J. Gettens, G.L. Stout, Painting Materials, A Short Encyclopaedia, Dover Publications, New York, 1966 Comment: density=2.93 ref. index=1.570; 1.614; 1.575
  • G.S.Brady, Materials Handbook, McGraw-Hill Book Co., New York, 1971
  • C.W.Chesterman, K.E.Lowe, Audubon Society Field Guide to North American Rocks and Minerals, Alfred A. Knopf, New York, 1979

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