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[1] to an oxychloride, DyOCl.
DyCl3 is often prepared by the "ammonium chloride route", starting from either Dy2O3 or the hydrated chloride DyCl3·6H2O.[2] [3] [4] These methods produce (NH4)2[DyCl<sub>5</sub>]:
10 NH4Cl + Dy2O3 → 2 (NH4)2[DyCl<sub>5</sub>] + 6 NH3 + 3 H2O
DyCl3·6H2O + 2 NH4Cl → (NH4)2[DyCl<sub>5</sub>] + 6 H2O
The pentachloride decomposes thermally according to the following equation:
(NH4)2[DyCl<sub>5</sub>] → 2 NH4Cl + DyCl3The thermolysis reaction proceeds via the intermediacy of (NH4)[Dy<sub>2</sub>Cl<sub>7</sub>].
Treating Dy2O3 with aqueous HCl produces the hydrated chloride DyCl3·6H2O, which cannot be rendered anhydrous by heating. Instead one obtains an oxychloride:[3]
DyCl3 + H2O → DyOCl + 2 HCl
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 other dysprosium(III) compounds, for example dysprosium(III) fluoride:
DyCl3 + 3 NaF → DyF3 + 3 NaCl
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.[5]
Dysprosium compounds are believed to be of low to moderate toxicity, although their toxicity has not been investigated in detail.