Thallous Silicates

Thallous oxide or carbonate reacts with silicic acid after the manner of the corresponding sodium and potassium compounds. A crystalline silicate of the composition 3Tl₂O.2SiO₂.H₂O has been described by Wyrouboff.

Thallium enters into the composition of various kinds of optical glass of high refractive index. High refractive power is a general characteristic of thallium salts.

Thallous silicofluoride, Tl₂SiF₆, is prepared from thallous carbonate and hydrofluosilicic acid, and crystallises from aqueous solution in colourless octahedra. According to Ruhlmann, the salt is volatile without decomposition, and crystallises from aqueous solution in hydrated form.