Phosphine

Phosphine

Names
IUPAC name Phosphane
Other names Phosphamine Phosphorus trihydride Phosphorated hydrogen
Identifiers
Jmol-3D images	Image
SMILES P
Properties
Chemical formula	PH3
Molar mass	33.99758 g/mol
Appearance	Colorless gas
Odor	Garlic-like Decayed fish-like
Density	1.379 g/l, gas (25 °C)
Melting point	−132.8 °C (−207.0 °F; 140.3 K)
Boiling point	−87.7 °C (−125.9 °F; 185.5 K)
Solubility in water	31.2 mg/100 ml (at 17 °C)
Solubility	soluble in alcohol, carbon disulfide, diethyl ether slightly soluble in benzene, chloroform, ethanol
Vapor pressure	41.3 atm (at 20°C)
Thermochemistry
Std molar entropy (So298)	210 J·mol−1·K−1
Std enthalpy of formation (ΔfHo298)	5 kJ·mol−1
Hazards
Safety data sheet	Praxair
Lethal dose or concentration (LD, LC):
LD50 (Median dose)	3.03 mg/kg (rat, oral)
LC50 (Median concentration)	11 ppm (rat, 4 hr)
Related compounds
Related compounds	Diphosphane
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
Infobox references

Phosphine or phosphane is a chemical compound of phosphorus. It is the phosphorus analogue of ammonia, with the chemical formula PH₃, although the chemical properties of the two compounds are very different.

Properties

Chemical

Phosphine may ignite in open air, although its pyrophoricity is influenced by other impurities, such as diphosphane.

Physical

Phosphine is a colorless gas, heavier than air and with a strong unpleasant smell, described as being garlic-like, decayed fish-like or sometimes even like that of burned rock, the smell being influenced by the various contaminants, depending on the source of phosphine. Unlike ammonia, phosphine is almost insoluble in water, but more soluble in various organic solvents, like ether or alcohols.

Availability

Phosphine is not available to the general public due to its very high toxicity. However, phosphides of certain metals are sometimes sold as pest control agents, and their reaction with water releases phosphine.

Preparation

The reaction of aluminium phosphide or any other phosphide with water releases phosphine gas. This reaction is used to kill most vermin in grain silos.

The most convenient way of obtaining phosphine is through the reaction of elemental phosphorus with a strong basic solution, such as sodium or potassium hydroxide:

2 P + 6 KOH + 3 H₂O → PH₃ + 3 KH₂PO₂

Reduction of phosphorus trichloride with lithium aluminium hydride in anhydrous diethyl ether yields phosphine.

Reduction of phosphorus pentoxide with hydrogen in the presence of a nickel catalyst results in phosphine.

Thermal decomposition of hypophosphorous acid (H₃PO₂) also yields phosphine.

Heating piperidine with red phosphorus in hydrogen will release phosphine.

Phosphine tends to be an unwanted product in various reactions involving phosphorus or phosphorus compounds. The most common way phosphine is encountered is in the reaction of impure calcium carbide with water. In industry, calcium carbide is made by roasting calcium oxide, obtained from rocks, such as calcium carbonate or calcium sulfate. This form of calcium tends to be contaminated with calcium phosphate, which is reduced at high temperatures to calcium phosphide, which in the presence of water hydrolyzes to yield phosphine.

It's recommended you avoid experimenting with phosphine, as, apart from its high toxicity, the phosphine smell is associated with meth labs, and its presence may draw the unwanted attention of the authorities.

Projects

Do something else! Phosphine's main use is to kill vermin from grain silos, and it doesn't have other uses.

Handling

Safety

Phosphine is extremely toxic and may cause death if inhaled even in low doses.

Storage

Do not store phosphine! Ever!

Disposal

Phosphine will eventually oxidize in open air to phosphorus pentoxide and phosphoric acid. Hydrogen peroxide is also good for neutralizing it. Bleach can also be used.

References

Relevant Sciencemadness threads

• Phosphine and white P from sodium hypophosphite?
• H3PO4 + Al = phosphine ?