Holmium(III) chloride

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. 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:


 * 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:


 * 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. 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.