Silicon tetraiodide, Si14, is formed by passing iodine vapour mixed with carbon dioxide over strongly-heated silicon (C. Friedel, Comptes rendus, 1868, 67, p. 98); the iodo-compound condenses in the colder portion of the apparatus and is purified by shaking with carbon bisulphide and with mercury.
The hexaiodide, S12161 is obtained by heating the tetraiodide with finely divided silver to 300° C. It crystallizes in hexagonal prisms which exhibit double refraction.
It is soluble in carbon bisulphide, and is decomposed by water and also by heat, in the latter case yielding the tetraiodide and the di-iodide, Si 2 I 4, an orange-coloured solid which is not soluble in carbon bisulphide.
Silicon iodoform, SiHI 3, is formed by the action of hydriodic acid on silicon, the product, which contains silicon tetraiodide, being separated by fractionation.
The tetraiodide, TiI 4, is a reddish brown mass having a metallic lustre.