Aluminium phosphide

Aluminium phosphide (AlP) is a compound of aluminium and phosphorus. It is a grey-green to green-yellow solid which reacts with moisture and acids to release phosphine. CAS registry number 20859-73-8.

AlP is used as a rodenticide, insecticide and fumigant for stored cereal grains. It is used to kill small verminous mammals such as moles, rabbits and rodents. In contact with water or acids, it releases phosphine, which acts as a fumigant; with acids, the reaction is much faster. The tablets or pellets typically also contain other chemicals which evolve ammonia which helps to reduce the potential for spontaneous ignition or explosion of the phosphine gas. They also contain other agents, such as methanethiol, to give the gas a detectable garlic smell to help warn against its presence in the atmosphere.

Metal phosphides have been used as a means of killing rodents. A mixture of food and aluminium 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 phosphine gas. This method of vermin control has possible use in places where rodents immune to many of the common poisons have appeared. Other pesticides similar to aluminium phosphide are zinc phosphide and calcium phosphide.

As a rodenticide, aluminium phosphide can be encountered under names eg. Celphos, Phostoxin, and Quick Phos.

Industrially, AlP is used in the semiconductor industry as a semiconductor material, usually combined with other elements to make more stable semiconductor alloys for applications in devices such as light-emitting diodes (e.g. aluminium gallium indium phosphide).