Thallium Tungstocyanide, Tl₄[W(CN)₈]

Thallium Tungstocyanide, Tl₄[W(CN)₈], is obtained by double decomposition from potassium tungstocyanide and a thallium salt. It forms long yellow needles which become red in sunlight but regain their yellow colour when heated. The salt is only sparingly soluble in cold water, but more readily soluble in hot.