Thallium sesqui-iodide, Tl₂I₃

Thallium sesqui-iodide, Tl₂I₃ or 3TlI.TlI₃, has been described by Knosel. The compound Tl₃I₄, or 5TlI.TlI₃, was discovered by Strecker, and, later, prepared by Jorgensen. It has been shown by Abegg and Maitland that thallous iodide passes into this compound at 25° in the presence of a solution of iodine in water or potassium iodide solution, provided that the concentration of free iodine in the liquid phase exceeds 0.0019 gram per litre, but does not exceed 0.082 gram per litre. When the concentration of free iodine exceeds the latter value, the compound Tl₃I₄ passes into thallic iodide. The compound Tl₃I₄ is a black solid, sparingly soluble in water and organic liquids with partial decomposition.