Platinum Di-iodide, PtI₂

Platinous Iodide, Platinum Di-iodide, PtI₂, may be obtained by warming a solution of potassium iodide with platinous chloride. The method is not altogether satisfactory because of the difficulty of deciding when the reaction is complete. If the heating is too prolonged the platinous iodide is converted into the platinic salt, PtI₄, and free platinum, the former of which passes into solution, whilst the latter contaminates the deposited di-iodide. On the other hand, if the reaction is not carried to completion the product is mixed with unattacked dichloride.

As prepared by the foregoing method, however, platinum di-iodide is obtained as a black, insoluble powder, stable in air. It is slowly soluble in hydriodic acid, but the solution undergoes decomposition into the tetra-iodide and metallic platinum. When heated to about 300° or 350° C. it dissociates into its components.