Tetrachlor~platinous Acid, H₂PtCl₄

Tetrachlor~platinous Acid, H₂PtCl₄, has not been isolated in a pure state, but exists in solution when platinous chloride is dissolved in hydrochloric acid, and when chlor-platinic acid is reduced by sulphur dioxide, the yellow solution becoming red in colour.

In dilute solution the pure acid results on decomposing the barium or silver salt with the requisite amount of sulphuric or hydrochloric acid. The solution cannot be concentrated, however, without decomposition, hydrogen chloride being evolved. When evaporated in vacuo, a residue of hydrated acid dichloride or trichlor-hydroxy-platinous acid is left, namely, PtCl₂.HCl.2H₂O or H₂PtCl₃(OH).H₂O. If the evaporation is continued at 100° C. platinous chloride results.