Preparation and Occurrence
Phosphine may be prepared in a variety of ways. Industrially it can be made by the reaction of white phosphorus with sodium hydroxide, producing sodium hypophosphite and sodium phosphite as a by-product. Alternatively the acid-catalyzed disproportioning of white phosphorus may be used, which yields phosphoric acid and phosphine. Both routes have industrial significance; the acid route is preferred method if further reaction of the phosphine to substituted phosphines is needed. The acid route requires purification and pressurizing. It can also be made (as described above) by the hydrolysis of a metal phosphide, such as aluminium phosphide or calcium phosphide. Pure samples of phosphine, free from P2H4, may be prepared using the action of potassium hydroxide on phosphonium iodide (PH4I).
Phosphine is probably a constituent of the atmosphere at very low and highly variable concentrations and hence may contribute to the global phosphorus biochemical cycle. The origin(s) of atmospheric phosphine is not certain. Possible sources include bacterial reduction of phosphate in decaying organic matter and the corrosion of phosphorus-containing metals.
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