Thallium(I) iodide, also known as thallous iodide, is a chemical compound. Its chemical formula is TlI. It has thallium and iodide ions in it. The thallium is in its +1 oxidation state.
Thallium(I) iodide is a yellow solid. It does not dissolve in water. It turns red when heated gently. It is a reducing agent. It is very toxic like all thallium compounds.
It is made by reacting thallium with iodine or hydroiodic acid or by reacting any soluble thallium salt like thallium(I) sulfate with any iodide.
Thallium(I) iodide is used in mercury-vapor lamps. It is also used in a detector of radiation.