Dysprosium(III) chloride (DyCl<sub>3</sub>), 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, DyCl<sub>3</sub>·6H<sub>2</sub>O. Simple rapid heating of the hydrate causes partial hydrolysis to an oxychloride, DyOCl.
Preparation and reactions
DyCl<sub>3</sub> is often prepared by the "ammonium chloride route", starting from either Dy<sub>2</sub>O<sub>3</sub> or the hydrated chloride DyCl<sub>3</sub>·6H<sub>2</sub>O. These methods produce (NH<sub>4</sub>)<sub>2</sub>[DyCl<sub>5</sub>]:
:10 NH<sub>4</sub>Cl + Dy<sub>2</sub>O<sub>3</sub> → 2 (NH<sub>4</sub>)<sub>2</sub>[DyCl<sub>5</sub>] + 6 NH<sub>3</sub> + 3 H<sub>2</sub>O
:DyCl<sub>3</sub>·6H<sub>2</sub>O + 2 NH<sub>4</sub>Cl → (NH<sub>4</sub>)<sub>2</sub>[DyCl<sub>5</sub>] + 6 H<sub>2</sub>O
The pentachloride decomposes thermally according to the following equation:
:(NH<sub>4</sub>)<sub>2</sub>[DyCl<sub>5</sub>] → 2 NH<sub>4</sub>Cl + DyCl<sub>3</sub>
The thermolysis reaction proceeds via the intermediacy of (NH<sub>4</sub>)[Dy<sub>2</sub>Cl<sub>7</sub>].
Treating Dy<sub>2</sub>O<sub>3</sub> with aqueous HCl produces the hydrated chloride DyCl<sub>3</sub>·6H<sub>2</sub>O, which cannot be rendered anhydrous by heating. Instead one obtains an oxychloride:
Precautions
Dysprosium compounds are believed to be of low to moderate toxicity, although their toxicity has not been investigated in detail.