Calcium Sulfate

CAS #: 7778-18-9; 10101-41-4 (dihydrate; 10034-76-1 (hemihydrate)

Synonyms: anhydrite (natural form); calcium sulfonate; anhydrous gypsum;Calcium salt of sulfuric acid; Calcium Sulphate; Sulfuric acid calcium salt.

Uses: Portland-cement retarder; tile and plaster; source of sulfer and sulfuric acid; polishing powders; paints (white pigments, filler, drier); paper (size filler, surface coating); dyeing and calico printing; metallurgy ( reduction of zinc minerals); drying industrial gases, solids, and many organic liquids; in granulated form as soil conditioner; quick setiing cements, molds, and surgical casts; wallboard; food additivr; desiccant.

Hazard:  Irritation to eyes, skin, upper respiratory system; conjunctivitis; rhinitis, epistaxis (nosebleed)  CALCIUM SULFATE is non-combustible. Decomposes to give toxic oxides of sulfur, but only at very high temperature (>1500°C). Generally of low reactivity but may act as an oxidizing agent: incompatible with diazomethane, aluminum, and phosphorus.  Certain forms of calcium sulfate react with water; others do not.  INSOLUBLE ANHYDRITE or dead-burned gypsum is made by the dehydration of calcium sulfate dihydrate (gypsum) at high (> 600°C) temperature.  At room temperature, insoluble anhydrite dissolves very slowly to the extent of 0.24 g per 100 g of water and does not absorb moisture from the air.  SOLUBLE ANHYDRITE, which is obtained by heating calcium sulfate dihydrate at a temperature below 300°C, has a high affinity for water and is used as a desiccant.  Soluble anhydrite absorbs water to form calcium sulfate hemihydrate (Plaster of  Paris).