Calcium Sulfate

calcium sulfate [′kal·se·əm ′səl‚fāt]

(inorganic chemistry)

CaSO₄A white crystalline salt, insoluble in water; used in Keene's cement, in pigments, as a paper filler, and as a drying agent.

Either of two hydrated forms of the salt: the dihydrate, CaSO₄·2H₂O, and the hemihydrate, CaSO₄·½H₂O.

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calcium sulfate

Anhydrite or gypsum dihydrate which has been calcined to the point at which all the water of crystallization has been removed.

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Calcium Sulfate 

CaSO₄, a salt, existing in nature as the dihydrate CaSO₄-2H₂O (gypsum, selenite) and in an anhydrous state (anhydrite). Anhydrous calcium sulfate occurs in the form of colorless crystals with a density of 2.96 g/cm³ and a melting point of 1450°C. It combines very slowly with water, exhibiting a poor solubility of 0.2036 g per 100 g H₂O at 20°C and 0.067 g at 100°C. The half-hydrate CaSO₄-1/2 H₂O is known; when mixed with water, it hardens rapidly, converting into CaSO_4««2H₂O. Calcium sulfate is used in the manufacture of figures and casts, as a construction material, and in medicine.