Arsenic trichloride

Arsenic trichloride is the chemical compound with the formula AsCl3. This colourless liquid is a starting reagent for the synthesis of organoarsenic compounds, such as triphenylarsine.

It is prepared by treatment of arsenic(III) oxide with concentrated hydrochloric acid followed by distillation:


 * As2O3 + 6 HCl  →  2 AsCl3  + 3 H2O

Thus, in contrast to PCl3, this compound has increased stability in the presence of acidic water. It undergoes a redistribution with As2O3 and AsCl3 gives the linear polymer AsOCl. With chloride sources, AsCl3, forms salts containing the anion [AsCl4]−.