Calcium phosphide (CP) is the

inorganic compound An inorganic compound is typically a chemical compound that lacks carbon–hydrogen bonds⁠that is, a compound that is not an organic compound. The study of inorganic compounds is a subfield of chemistry known as ''inorganic chemistry''. Inorgan ...

with the formula Ca₃P₂. It is one of several phosphides of calcium, being described as the salt-like material composed of Ca²⁺ and P³⁻. Other, more exotic calcium phosphides have the formula CaP / Ca₂P₂, CaP₃, and Ca₅P₈. Ca₃P₂ 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.

Preparation, history and structure

It may be formed by reaction of the elements, but it is more commonly prepared by carbothermal reduction of calcium phosphate: :Ca₃(PO₄)₂ + 8 C → Ca₃P₂ + 8 CO This is also the way how it was accidentally discovered by Smithson Tennant in 1791 while verifying the composition of

carbon dioxide Carbon dioxide is a chemical compound with the chemical formula . It is made up of molecules that each have one carbon atom covalent bond, covalently double bonded to two oxygen atoms. It is found in a gas state at room temperature and at norma ...

proposed by

Antoine Lavoisier Antoine-Laurent de Lavoisier ( ; ; 26 August 17438 May 1794), When reduced without charcoal, it gave off an air which supported respiration and combustion in an enhanced way. He concluded that this was just a pure form of common air and that i ...

by reducing

calcium carbonate Calcium carbonate is a chemical compound with the chemical formula . It is a common substance found in Rock (geology), rocks as the minerals calcite and aragonite, most notably in chalk and limestone, eggshells, gastropod shells, shellfish skel ...

with phosphorus. The structure of the room temperature form of Ca₃P₂ has not been confirmed by X-ray crystallography. A high temperature phase has been characterized by Rietveld refinement. Ca²⁺ centers are octahedral.

Uses

Metal phosphides are used as a rodenticide. A mixture of food and calcium phosphide is left where the rodents can eat it. The acid in the digestive system of the rodent reacts with the phosphide to generate the toxic gas

phosphine Phosphine (IUPAC name: phosphane) is a colorless, flammable, highly toxic compound with the chemical formula , classed as a pnictogen hydride. Pure phosphine is odorless, but technical grade samples have a highly unpleasant odor like rotting ...

. This method of vermin control has possible use in places where rodents immune to many of the common warfarin-type ( anticoagulant) poisons have appeared. Other pesticides similar to calcium phosphide are zinc phosphide and aluminium phosphide. Calcium phosphide is also used in

fireworks Fireworks are Explosive, low explosive Pyrotechnics, pyrotechnic devices used for aesthetic and entertainment purposes. They are most commonly used in fireworks displays (also called a fireworks show or pyrotechnics), combining a large numbe ...

, torpedoes, self-igniting naval pyrotechnic flares, and various water-activated ammunition. During the 1920s and 1930s, Charles Kingsford Smith used separate buoyant canisters of calcium carbide and calcium phosphide as naval flares lasting up to ten minutes. It is speculated that calcium phosphide—made by boiling bones in urine, within a closed vessel—was an ingredient of some ancient Greek fire formulas. Calcium phosphide is a common impurity in calcium carbide, which may cause the resulting phosphine-contaminated

acetylene Acetylene (Chemical nomenclature, systematic name: ethyne) is a chemical compound with the formula and structure . It is a hydrocarbon and the simplest alkyne. This colorless gas is widely used as a fuel and a chemical building block. It is u ...

to ignite spontaneously.

References

{{DEFAULTSORT:Calcium Phosphide Phosphides Calcium compounds Rodenticides Fumigants

Preparation, history and structure

Uses

See also

References