Calcium phosphide Calcium phosphide Calcium phosphide (CP) is the inorganic compound with the formula CaP. It is one of several phosphides of calcium, being described as the salt-like material composed of Ca and P. Other, more exotic calcium phosphides have the formula CaP, CaP, CaP, and CaP. CaP has the appearance of red-brown crystalline powder or grey lumps. Its trade name is Photophor for the incendiary use or Polytanol for the use as rodenticide. It may be formed by reaction of the elements, but it is more commonly prepared by carbothermal reduction of calcium phosphate: The structure of the room temperature form
Calcium carbonate Calcium carbonate shares the typical properties of other carbonates. Notably, Calcium carbonate will react with water that is saturated with carbon dioxide to form the soluble calcium bicarbonate. This reaction is important in the erosion of carbonate rock, forming caverns, and leads to hard water in many regions. An unusual form of calcium carbonate is the hexahydrate, ikaite, CaCO·6HO. Ikaite is stable only below 8 °C. The vast majority of calcium carbonate used in industry is extracted by mining or quarrying. Pure calcium carbonate (e.g. for food or pharmaceutical use), can be produced from a pure quarried source (usually marble).