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