Platinum Sesquioxide, Pt₂O₃

Hydrated Platinum Sesquioxide, Pt₂O₃.xH₂O, may be obtained by decomposing the trichloride, PtCl₃, with a hot solution of sodium carbonate; it also results on acidifying with acetic acid a solution of the trichloride in potassium hydroxide solution.

Hydrated platinum sesquioxide is a brown substance, insoluble in water, but soluble both in concentrated sulphuric acid and in caustic alkali solutions. When dehydrated in vacuo, it decomposes, so that the anhydrous sesquioxide has not been obtained.