Tetrachlor-dihydroxy-platinic Acid, H₂PtCl₄(OH)₂

Tetrachlor-dihydroxy-platinic Acid, H₂PtCl₄(OH)₂ or PtCl₄.2H₂O, is obtained in solution by hydrolysing silver hexaehlor-platinate with boiling water:

Ag₂PtCl₆ + 2H₂O = 2AgCl + H₂PtCl₄(OH)₂,

and exists in solution when platinum tetrachloride is dissolved in water.

Upon concentrating the solution and heating the residue to 100° C. the monohydrate of platinic chloride, PtCl₄.H₂O, is obtained. Further dehydration cannot be effected in this manner without decomposition of the salt.

The solution has an acid reaction, decomposing carbonates. Titration with alkali, using phenolphthalein as indicator, shows that the acid is dibasic.

Several salts of this acid have been prepared. The silver salt, Ag₂PtCl₄(OH)₂, has long been known. Other salts are those of zinc, ZnPtCl₄(OH)₂.3H₂O; cadmium, CdPtCl₄(OH)₂; lead, PbPtCl₄(OH)₂, and a basic lead salt, PbPtCl₄(OH)₂.Pb(OH)₂.