Tin Phosphides

Several well-defined phosphides of tin have been made by the dry methods. The early work was of a qualitative nature. Phosphides of tin may be made by heating metaphosphoric acid or a phosphate and silica with carbon and tin or stannic oxide.

When phosphorus and tin are melted together in a sealed tube, two liquid layers are formed, and the maximum amount of phosphorus taken up by the tin is 8 per cent., while by heating tin and phosphorus in a sealed tube at 620° C. for 10 hours grey crystals were obtained which contained 40 per cent, of phosphorus and which after purification by hydrochloric acid, alkali and nitric acid had the composition SnP₃. The density was 4.1 at 0° C. Alloys of tin with about 13 per cent, of phosphorus contained Sn₄P₃, which had a density of 5.18 and was attacked by aqueous acids.

Commercial phosphor-tin may contain up to 10 per cent, of phosphorus as phosphides, the crystals of which are revealed by etching with dilute nitric acid. Phosphor-tin is much used for making phosphor-bronzes.

The action of phosphine on tin salts also gives phosphide.