Platinum Tungstates

Only complex salts are known. When platinic hydroxide is boiled with a solution of an alkali tungstate, yellow needle-shaped crystals separate which show the reactions of a paratungstate. The composition of the product is 5Na₂O.2PtO₂. 7WO₃.35H₂O, but it cannot be recrystallised and is probably a double salt of sodium paratungstate and sodium platinate, 3Na₂O.7WO₃ + 2(Na₂O.PtO₂).35H₂O. By using paratungstates of the alkali metals, Gibbs obtained a series of crystalline products which appeared to be complex platino-tungstates. According to Rosenheim, however, they were alkali paratungstates containing occluded platinic hydroxide.