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 with the symbol Ge and atomic number 32. It is lustrous, hard-brittle, grayish-white and similar in appearance to silicon. It is a metalloid in the carbon group that is chemically similar to its group neighbors s ...

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

fiber optic An optical fiber, or optical fibre in Commonwealth English, is a flexible, transparent fiber made by drawing glass (silica) or plastic to a diameter slightly thicker than that of a human hair. Optical fibers are used most often as a means to ...

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 Vitrain is a type of coal. Its combustion leads to ash containing extractable levels of germanium compounds such as germanium dioxide Germanium dioxide, also called germanium(IV) oxide, germania, and salt of germanium, is an inorganic compound ...

. 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 Germanium dioxide, also called germanium(IV) oxide, germania, and salt of germanium, is an inorganic compound with the chemical formula Ge O2. It is the main commercial source of germanium. It also forms as a passivation layer on pure germani ...

) 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 Sodium chlorate is an inorganic compound with the chemical formula Na ClO3. It is a white crystalline powder that is readily soluble in water. It is hygroscopic. It decomposes above 300 °C to release oxygen and leaves sodium chloride. Sever ...

. 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. Aditionally, a chlorine free activation of germanium has been devloped, 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

. In the manufacture of

optical fibers An optical fiber, or optical fibre in Commonwealth English, is a flexible, transparent fiber made by drawing glass (silica) or plastic to a diameter slightly thicker than that of a human hair. Optical fibers are used most often as a means ...

silicon tetrachloride Silicon tetrachloride or tetrachlorosilane is the inorganic compound with the formula SiCl4. It is a colourless volatile liquid that fumes in air. It is used to produce high purity silicon and silica for commercial applications. Preparation Silic ...

, SiCl₄, and germanium tetrachloride, GeCl₄, are introduced with

oxygen Oxygen is the chemical element with the symbol O and atomic number 8. It is a member of the chalcogen group in the periodic table, a highly reactive nonmetal, and an oxidizing agent that readily forms oxides with most elements as wel ...

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 In optics, the refractive index (or refraction index) of an optical medium is a dimensionless number that gives the indication of the light bending ability of that medium. The refractive index determines how much the path of light is bent, or ...

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