Holmium(III) chloride explained

Holmium(III) chloride is the inorganic compound with the formula HoCl₃. It is a common salt but is mainly used in research. It can be used to produce pure holmium.^[1] It exhibits the same color-changing behavior seen in holmium oxide, being a yellow in natural lighting and a bright pink color in fluorescent lighting.

Preparation

The most commonly used method to obtain holmium(III) chloride involves heating a mixture of holmium(III) oxide and ammonium chloride at 200-250 °C:^[2]

Ho₂O₃ + 6 NH₄Cl → 2 HoCl₃ + 6 NH₃ + 2 H₂O

The hexahydrate of holmium(III) chloride can be obtained by reaction between holmium and hydrochloric acid:

2 Ho + 6 HCl → 2 HoCl₃ + 3 H₂

It can also be prepared by the direct reaction between holmium and chlorine:^[3]

2 Ho + 3 Cl₂ → 2 HoCl₃

Properties

Holmium(III) chloride and its hexahydrate are light yellow solids in daylight that are soluble in water. The hexahydrate starts to release water of crystallization at 64 °C.^[4] Holmium(III) chloride has a monoclinic crystal structure analogous to that of aluminum(III) chloride. In the solid state it has the YCl₃ layer structure.^[5]

Notes and References

1. Book: Emsley, John . Nature's building blocks: an A-Z guide to the elements . 2003 . Oxford Univ. Press . 978-0-19-850340-8 . Reprinted with corrections . Oxford.
2. Handbook of Preparative Inorganic Chemistry, 2nd Ed. Edited by G. Brauer, Academic Press, 1963, NY.
3. Webelements: Holmium
4. Book: Ans, Jan d' . Elemente, anorganische Verbindungen und Materialien . Ans . Jan d' . 1998 . Verlag nicht ermittelbar . 978-3-540-60035-0 . 4., neubearb. u. rev. Aufl . Taschenbuch für Chemiker und Physiker / D'Ans . Ort nicht ermittelbar.
5. Wells A.F. (1984) Structural Inorganic Chemistry 5th edition Oxford.