Thallous chromate, Tl₂CrO₄

Thallous chromate, Tl₂CrO₄, is precipitated when a solution of a thallous salt is mixed with potassium chromate. It is also produced by adding thallous hydroxide or carbonate to aqueous chromic acid, or by the action of ammonia on the dichromate. Thallous chromate is a yellow crystalline powder, very sparingly soluble in water, 100 grams of which dissolve 0.03 gram of the salt at 60° and 0.2 gram at 100°. In hot, concentrated potassium hydroxide solution thallous chromate is fairly soluble, and it separates out on cooling in crystals which are apparently isomorphous with potassium chromate. At a dull red heat the chromate melts, and at higher temperatures it loses oxygen.