Thallic hydroxide, TlO.OH

Thallic hydroxide, TlO.OH or Tl₂O₃.H₂O, is obtained by precipitating a solution of a thallic salt with a slight excess of alkali hydroxide or ammonia, washing the precipitate, and drying it at the ordinary temperature in the air. It is also produced by the action of alkali hypochlorite on an alkaline solution of a thallous salt.

Thallic hydroxide is a reddish-brown powder. When heated to 110°-120° it is completely dehydrated to thallic oxide, and it is also dehydrated when heated in contact with the liquid from which it has been precipitated. The freshly precipitated hydroxide reacts readily with acids; but, after it has been dried, solution in acids is slow, and is accompanied by partial reduction. The hydroxide is practically insoluble in water.