Potassium Tetrachlor-platinite, K₂PtCl₄

Potassium Tetrachlor-platinite, K₂PtCl₄, is obtained technically by passing sulphur dioxide into a solution of chlor-platinic acid, maintained at about 100° C., until a sample yields no precipitate with ammonium chloride. This indicates that reduction is complete. A hot solution of twice the calculated quantity of potassium chloride is added, and the chlor-platinite allowed to crystallise out. It is washed with alcohol and dried in the absence of light.

Although a solution of pure potassium hexachlor-platinate, K₂PtCl₆, is not reduced by boiling with potassium oxalate, reduction readily takes place if a trace of iridium in solution is added. In the presence of much iridium the reaction may even become violent.

The density of potassium tetrachlor-platinite is 3.3056 at 20.3° C., and 3.2909 at 21° C., whilst its heat of formation is:

[Pt] + (Cl₂) + 2[KCl] = [K₂PtCl₄] + 45.17 Cals.