Platinum Dichloride, PtCl2, also known as Platinous Chloride, may be prepared by evaporating a solution of the tetrachloride to dryness and heating the residue to about 300° or 350° C. under constant stirring. Any unchanged platinic acid is removed by washing with water.
Platinum dichloride also results, mixed with a little tetrachloride, when platinum sponge or, better, platinum black, obtained by reduction of ammonium chlor-platinate by hydrogen gas at 100° C., is heated in chlorine to 360° C. It is obtained in a more pure condition by heating chlor-platinous acid, H2PtCl4, or the hydrated acid chloride, namely, trichlor-platinous acid, PtCl2.HCl.2H2O or H2PtCl3(OH)H2O, to 100° C.
Platinum dichloride is a greenish grey or brown powder, its colour varying according to the method of preparation. Insoluble in water, it dissolves in hydrochloric acid to yield a solution of chlor-platinous acid, H2PtCl4, and in aqua regia to chlor-platinic acid, H2PtCl6. Caustic alkalies decompose it, yielding a black deposit of hydrated platinous oxide. With ammonia, complex ammino derivatives are formed. |