Holmium(III) iodide explained

Holmium(III) iodide is an iodide of holmium, with the chemical formula of HoI₃. It is used as a component of metal halide lamps.^[1]

Preparation

Holmium(III) iodide can be obtained by directly reacting holmium and iodine:

2 Ho + 3 I₂ → 2 HoI₃

Holmium(III) iodide can also be obtained via the direct reaction between holmium and mercury(II) iodide:

2 Ho + 3 HgI₂ → 2 HoI₃ + 3 Hg

The mercury produced in the reaction can be removed by distillation.^[2]

Holmium(III) iodide hydrate can be converted to the anhydrous form by dehydration with a large excess of ammonium iodide (since the compound is prone to hydrolysis).^[3]

Properties

Holmium(III) iodide is a highly hygroscopic substance that dissolves in water.^{[4] [5] [6]} 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.

Notes and References

1. Book: Flesch, Peter G. . [{{Google books URL|fWHQbhgxpAkC|page=45}} Light and Light Sources: High-Intensity Discharge Lamps]. Springer. 2007. 45. 978-3540326854.
2. 10.1021/ic50018a015. Preparation and crystal data for lanthanide and actinide triiodides. 1964. Asprey. L. B.. Keenan. T. K.. Kruse. F. H.. Inorganic Chemistry. 3. 8. 1137–1141.
3. [Georg Brauer]
4. Web site: Holmium triiodide . WebElements . 2022-08-20.
5. Book: Carl L. Yaws. The Yaws Handbook of Physical Properties for Hydrocarbons and Chemicals. Gulf Professional Publishing. 2015. en. 2017-08-28. 301. 978-0128011461.
6. Web site: 13635 Holmium(III) iodide, ultra dry, 99.99% (REO) . Alfa Aesar . 2022-08-20.