Thallium Orthothioarsenate, Tl₃AsS₄

Thallium Orthothioarsenate, Tl₃AsS₄, may be obtained by passing hydrogen sulphide into an alkaline solution containing an arsenate and a thallous salt. It forms an orange-coloured precipitate, decomposed by acids and on boiling with concentrated alkali sulphides. It is stable in air, but undergoes partial decomposition on heating.