Platinum Triselenide, PtSe₃

Platinum Triselenide, PtSe₃, has been obtained as a black, flocculent precipitate by reduction with formaldehyde of a solution of an alkali chlor-platinate in the presence of a selenite and an excess of alkali.

The reaction may be represented as follows:

K₂PtCl₆ + 3SeO₂ + 8HCHO + 12KOH = PtSe₃ + 6KCl + 8HCOOK + 10H₂O.

Upon heating to dull redness in a current of carbon dioxide, platinum triselenide is converted into the diselenide, PtSe₂, which is left as a greyish black powder.