Holmium(III) iodide


Holmium iodide is an iodide of holmium, with the chemical formula of HoI3. It is used as a component of metal halide lamps.

Preparation

Holmium iodide can be obtained by directly reacting holmium and iodine:
Holmium iodide can also be obtained via the direct reaction between holmium and mercury(II) iodide:
The mercury produced in the reaction can be removed by distillation.
Holmium iodide hydrate can be converted to the anhydrous form by dehydration with a large excess of ammonium iodide.

Properties

Holmium iodide is a highly hygroscopic substance that dissolves in water. It forms yellow hexagonal crystals with a crystal structure similar to bismuth(III) iodide. In air, it quickly absorbs moisture and forms hydrates. The corresponding oxide iodide is also readily formed at elevated temperature.