Products
Calcium sulfate and plaster bandages are available, for example, in pharmacies and drugstores.
Structure and properties
Calcium sulfate dihydrate (CaSO4 – 2 H2O, Mr = 172.2 g/mol) is the calcium salt of sulfuric acid. It exists in pharmaceutical grade as a white, odorless and fine powder that is very slightly soluble in water. Calcium sulfate dihydrate is also known as gypsum. Unlike many other substances, its solubility in water decreases with increasing temperature. It is a natural substance found in many minerals. The melting point is high at 1460 °C. Gypsum can be produced, for example, from calcium carbonate (lime) with the sulfuric acid:
- CaCO3 (calcium carbonate) + H2SO4 (sulfuric acid) + H2O (water) CaSO4 – 2 H2O (calcium sulfate dihydrate) + CO2 (carbon dioxide)
When dissolved in water, calcium sulfate dihydrate reacts neutrally (pH 7 with 50 g in 1000 ml). Calcium sulfate dissolves in various acids. If calcium sulfate is added to the hydrochloric acid, the readily water-soluble calcium chloride is formed:
- CaSO4 (calcium sulfate) + 2 HCl (hydrochloric acid) CaCl2 (calcium chloride) + H2SO4 (sulfuric acid)
Fields of application
- As a pharmaceutical excipient.
- For the manufacture of plaster bandages, for a plaster cast.
- As a food additive (eg for dough) and as a calcium additive for food.
- In alternative medicine under the obsolete name Calcium sulfuricum.
- For tinkering.
Plaster has a very great importance as a building material.
Undesirable effects
Calcium sulfate does not have a GHS hazardous substance label. Inhalation of gypsum dust should be avoided.
