Germanium tetrachloride

Most commercial production of germanium is from treating flue-dusts of zinc- and copper-ore smelters, although a significant source is also found in the ash from the combustion of certain types of coal called vitrain. Germanium tetrachloride is an intermediate for the purification of germanium metal or its oxide, GeO2. Germanium tetrachloride can be generated directly from GeO2 (germanium dioxide) by dissolution of the oxide in concentrated hydrochloric acid. : The resulting mixture is fractionally distilled to purify and separate the germanium tetrachloride from other products and impurities. The GeCl4 can be rehydrolysed with deionized water to produce pure GeO2, which is then reduced under hydrogen to produce germanium metal. Additionally, a chlorine free activation of germanium has been developed, giving a less energy intensive and more environmentally friendly alternative synthesis for germanium precursors. ==Application==

Germanium tetrachloride is used almost exclusively as an intermediate for several optical processes. GeCl4 can be directly hydrolysed to GeO2, an oxide glass with several unique properties and applications, described below and in linked articles: Fiber optics A notable derivative of GeCl4 is germanium dioxide. In the manufacture of optical fibers, silicon tetrachloride, SiCl4, and germanium tetrachloride, GeCl4, are introduced with oxygen into a hollow glass preform, which is carefully heated to allow for oxidation of the reagents to their respective oxides and formation of a glass mixture. The GeO2 has a high index of refraction, so by varying the flow rate of germanium tetrachloride the overall index of refraction of the optical fiber can be specifically controlled. The GeO2 is about 4% by weight of the glass. ==References==