Platinum Monoxide, PtO

Platinous Oxide, Platinum Monoxide, PtO, is produced in the anhydrous condition in the form of superficial blackening when platinum, either in the form of sponge or of thin foil, is heated in dry oxygen at about 450° C., the product containing as much as 43 per cent, of oxide.

It dissolves in hydrochloric acid containing a trace of platinous chloride, yielding this latter salt.

When heated, platinous oxide decomposes, yielding metallic platinum and its dioxide.

Hydrated Platinum Monoxide, PtO,2H₂O, is obtained in a more or less impure condition by the addition of warm potassium hydroxide solution to platinous chloride. The pure hydrated oxide, however, may be obtained by boiling a solution of potassium chlor-platinite with the calculated amount of sodium hydroxide solution. The hydrated oxide separates out as a dark precipitate, which is readily oxidised by exposure to air, so that it is necessary to wash and dry it in an atmosphere of carbon dioxide. It retains its combined water very tenaciously, and cannot be completely dehydrated without partial decomposition.

The freshly precipitated oxide is soluble in concentrated hydrochloric acid and in sulphurous acid. Concentrated nitric and sulphuric acids also effect its solution, but the dilute acids are practically without action. After drying in an exsiccator, however, hydrated platinum monoxide is insoluble in concentrated sulphuric or nitric acid. It dissolves, however, in concentrated hydrochloric acid.

The hydrated oxide possesses oxidising powers, arsenious acid being oxidised to arsenic acid, hydrogen iodide to iodine, whilst hydrogen gas raises the oxide to incandescence, water being formed.

The oxide is capable also of effecting certain reductions, hydrogen peroxide being reduced to water, and acidulated potassium permanganate to manganese dioxide, platinum dioxide being simultaneously formed.