What Is Calcium Sulfate?
Calcium sulfate, known for its primary role in gypsum, is an inorganic compound with the formula CaSO4. Appearing as a colorless to white crystal, it’s insoluble in water and found naturally in both dihydrate and anhydrate forms. Governed by various laws for chemical substance control, agricultural chemical control, and food sanitation, it is recognized for its utility and safety.
Uses of Calcium Sulfate
Its applications are diverse, ranging from food production, where it acts as a coagulant and additive, to agriculture as a calcium and sulfur fertilizer. In construction and medicine, it’s valued for its hardening properties, serving in ceramics, dental models, and casts for broken bones. Gypsum board, a recyclable material, is widely used in buildings for its excellent properties.
Properties of Calcium Sulfate
With a molecular weight of 136.14, a melting point of 1450°C, and solubility in concentrated sulfuric acid, calcium sulfate stands out for its chemical stability and versatility. It’s compatible with sodium thiosulfate and ammonium salts, forming complexes that extend its utility.
Types of Calcium Sulfate
Varied by water content, calcium sulfate presents as anhydrite or hard plaster in anhydrous form, hemihydrate with distinct structural types suitable for different applications, and dihydrate or soft plaster, often referred to as ordinary gypsum.
Other Information on Calcium Sulfate
How Calcium Sulfate is Produced
Calcium sulfate can be mined from natural ores or chemically synthesized. Chemically, calcium sulfate is obtained by the reaction of sulfuric acid and calcium content.
Calcium sulfate is also obtained in the wet phosphoric acid production process. Specifically, phosphate (Ca5(PO4)3・F) reacts with phosphoric acid (H3PO4) to yield water-soluble monocalcium phosphate (Ca(H2PO4)2) and hydrogen fluoride (HF). Sulfuric acid (H2SO4) is then added to produce phosphoric acid and calcium sulfate. The calcium phosphate obtained in this production process is also called gypsum phosphate. In addition to the phosphoric acid production process, calcium sulfate is also obtained as a byproduct of the flue gas desulfurization process and the titanium and hydrofluoric acid production processes.