Aluminium phosphide

Aluminium phosphide
Other names	Aluminium(III) phosphide Aluminium monophosphide Phostoxin Fumitoxin
Identifiers
InChI	InChI=1/Al.P/rAlP/c1-2
InChIKey	PPNXXZIBFHTHDM-LQQCNYPFAR
CAS number	[20859-73-8]
RTECS	BD1400000
ChemSpider	28171
PubChem	30332
SMILES	[Al]#P
Properties
Chemical formula	AlP
Molar mass	57.9552 g/mol
Appearance	yellow or gray crystals
Density	2.85 g/cm³, solid
Melting point	2530 °C
Solubility in water	reacts
Band gap	2.5 eV (indirect)
Refractive index (nD)	2.75 (IR), ~3 (Vis)
Hazards
Material safety data sheet (MSDS)	External MSDS
EU classification	Template:Hazchem T Template:Hazchem N
NFPA 704
Flash point	>800 °C
LD50	11.5 mg/kg
Template:Tick(what is this?)  (verify) Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa)

Aluminium phosphide is the chemical compound with the empirical formula AlP. This colourless solid is generally sold as a grey-green-yellow powder due to the presence of impurities arising from hydrolysis and oxidation. This material is a wide band gap semiconductor and is used as a fumigant.

Structure, synthesis, and chemical properties

AlP crystallizes in the cubic zinc blende lattice, wherein all atoms have tetrahedral coordination. Related materials crystallize similarly, including GaAs. At pressures of 14-17 GPa, AlP transforms into a rocksalt phase .

Crude aluminium phosphide can be prepared in the laboratory by igniting a mixture of red phosphorus and powdered aluminium.

Aluminium phosphide reacts with water or acids to release phosphine.

AlP + 3 H₂O → Al(OH)₃ + PH₃

AlP + 3 H⁺ → Al³⁺ + PH₃

Physical properties

Aluminium phosphide has a hardness of 5.5 on the Mohs scale .

Pesticide

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. The tablets or pellets typically also contain other chemicals that evolve ammonia which helps to reduce the potential for spontaneous ignition or explosion of the phosphine gas.

As a rodenticide, aluminium phosphide pellets are provided as a mixture with food for consumption by the rodents. The acid in the digestive system of the rodent reacts with the phosphide to generate the toxic phosphine gas. Other pesticides similar to aluminium phosphide are zinc phosphide and calcium phosphide.

As a rodenticide, aluminium phosphide can be encountered under various brand names, e.g. Celphos, Fumitoxin, Phostoxin, and Quick Phos.

Incidents

In October 2002, Sir Derek Bibby, 2nd baronet and great-great-grandson of the founder and past chairman and president of the Bibby Line shipping company, aged 80 and terminally ill with leukaemia, committed suicide by consuming aluminium phosphide - the poison, hours later, caused his body to emit dangerous fumes forcing the evacuation of the hospital department where his body was being held.

In February 2009, two children died in Jeddah, Saudi Arabia after a neighbouring house was fumigated with aluminium phosphide.

Semiconductor applications

Industrially, AlP is a semiconductor material that is usually alloyed with other binary materials for applications in devices such as light-emitting diodes (e.g. aluminium gallium indium phosphide).