Dysprosium(III) chloride

Dysprosium(III) chloride (DyCl3), also known as dysprosium trichloride, is a compound of dysprosium and chlorine. It is a white to yellow solid which rapidly absorbs water on exposure to moist air to form a hexahydrate, DyCl3.6H2O. Simple rapid heating of the hydrate causes partial hydrolysis to an oxychloride, DyOCl.

Chemical properties
Dysprosium(III) chloride is a moderately strong Lewis acid, which ranks as "hard" according to the HSAB concept. Aqueous solutions of dysprosium chloride can be used to prepare insoluble dysprosium(III) compounds, for example dysprosium(III) fluoride:


 * DyCl3(aq) +  3 NaF(aq) →  DyF3(s)  +  3 NaCl(aq)

Preparation
Dysprosium(III) chloride can be prepared as a yellow aqueous solution by reaction of either dysprosium metal or dysprosium(III) carbonate and hydrochloric acid.


 * 2 Dy(s) +  6 HCl(aq) → 2 DyCl3(aq) + 3 H2(g)


 * Dy2(CO3)3(s) +  6 HCl(aq)  →  2 DyCl3(aq)  +  3 CO2(g)  +  3 H2O(l)

Anhydrous DyCl3 can be made by dehydration of the hydrate either by slowly heating to 400 °C with 4-6 equivalents of ammonium chloride under high vacuum. The anhydrous halide may alternatively be prepared from dysprosium metal and hydrogen chloride. It is usually purified by high temperature sublimation under high vacuum.

Uses
Dysprosium(III) chloride can be used as a starting point for the preparation of other dysprosium salts. Dysprosium metal is produced when a molten mixture of DyCl3 in eutectic LiCl-KCl is electrolysed. The reduction occurs via Dy2+, at a tungsten cathode.

Precautions
Dysprosium compounds are believed to be of low to moderate toxicity, although their toxicity has not been investigated in detail.