Abstract: Electrodeposition is one of the clean methods to prepare elementary arsenic. In this paper, the theoretical solubility of As(Ⅲ) in aqueous solutiou was calculated, and the mechanism of forming AsH₃ in electrodeposition was analyzed. The research reveals that the solubility of As(Ⅲ) is significantly larger in aqueous alkali solution than in aqueous acid or neutral solution, which results that electrodepositing arsenic in alkali solution is much easier and that the efficient method to prevent forming AsH₃ is to enhance the electric potential of evolving hydrogen.

Key words: arsenic, aqueous solution, electrodeposition, AsH₃