Platinum Monosilicide, PtSi

Platinum Monosilicide, PtSi, may be obtained by igniting a mixture of finely divided silicon and platinum sponge at a high temperature. On treating the melt with potassium hydroxide solution, excess of silicon is removed, leaving a residue of monosilicide. When recrystallised from fused silver silicide, the latter being removed by extraction with sodium hydroxide and nitric acid in succession, the monosilicide is obtained as prismatic crystals, melting at about 1100° C., and of density 11.63 at 15° C.

The usual mineral acids, including all the halogen acids, are without action upon it, but aqua regia effects its solution, and concentrated hydrochloric acid containing bromine also attacks it.

When heated with copper silicide, Cu₄Si, it yields a double silicide, PtCu₂Si, as a dense grey substance, completely soluble in aqua regia.