Germanium tetrachloride is a colourless, fuming liquid with a peculiar, acidic odour. It is used as an intermediate in the production of purified

germanium Germanium is a chemical element; it has Symbol (chemistry), symbol Ge and atomic number 32. It is lustrous, hard-brittle, grayish-white and similar in appearance to silicon. It is a metalloid or a nonmetal in the carbon group that is chemically ...

metal. In recent years, GeCl₄ usage has increased substantially due to its use as a reagent for fiber optic production.

Production

Most commercial production of

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" Mineral Commodity Profile, U.S. Geological Survey, 2005. 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 Elements" C. R. Hammond, David R. Lide, ed. ''CRC Handbook of Chemistry and Physics'', Edition 85 (CRC Press, Boca Raton, Florida) (2004) The GeCl₄ can be rehydrolysed with deionized water to produce pure GeO₂, which is then reduced under hydrogen to produce germanium metal. Production of GeO₂, however, is dependent on the oxidized form of germanium extracted from the ore. Copper-lead-sulfide and zinc-sulfide ores will produce GeS₂, which is subsequently oxidized to GeO₂ with an oxidizer such as sodium chlorate. Zinc-ores are roasted and sintered and can produce the GeO₂ directly. The oxide is then processed as discussed above. The classic synthesis from chlorine and germanium metal at elevated temperatures is also possible. 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 Oxygen is a chemical element; it has chemical symbol, symbol O and atomic number 8. It is a member of the chalcogen group (periodic table), group in the periodic table, a highly reactivity (chemistry), reactive nonmetal (chemistry), non ...

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.

Production

Application

Fiber optics

References

See also