Germanium dioxide is prepared by heating germanium with oxygen at elevated temperatures, or by hydrolysis of germanium(IV) halides:
GeCl4 + 2H2O → GeO2 + 4HCl
It also is prepared by oxidation of germanium(II) sulfide:
GeS + 2O2 GeO2 + SO2
The product obtained in the above reactions is in the form of hexagonal modification of GeO2.
Germanium dioxide has high refractive index and infrared transmission,
for which it is used in industrial glasses. It also is used in preparation of high
purity grade germanium.
The oxide (GeO2) is usually prepared by hydrolysing redistilled GeCl4 and igniting it in order to remove H2O and chloride. It can be further purified by dissolving in hot H2O (solubility is 4g/L cold) evaporating and drying the residual crystalline solid. When the soluble form (which is produced in H2O at 355o) is heated for 100hours, it is converted to the insoluble form. This form is stable at temperatures up to 1033o, and fusion at 1080o for 4hours causes complete de-vitrification and it reverts to the soluble form. [Müller & Blank J Am Chem Soc 46 2358 1924, Dennis & Laubengayer J Am Chem Soc 47 1945 1925, Laubengayer & Morton J Am Chem Soc 54 2303 1932, Schenk in Handbook of Preparative Inorganic Chemistry (Ed. Brauer) Academic Press Vol I p 706 1963.]
Germanium dioxide is reduced to germanium metal when heated with hydrogen at 1,000°C:
GeO2 + 2H2 → Ge + 2H2O
When heated with germanium, the dioxide is reduced to monoxide, GeO:
GeO2 + Ge 2GeO
Treatment with hydrochloric acid yields germanium(IV) chloride:
GeO2 + 4HCl → GeCl4 + 2H2O
In a strongly acidic solution, its reaction with hydrogen sulfide yields an amorphous modification of germanium(IV) sulfide, GeS2.
Melting a mixture of germanium dioxide and metal oxides produces orthoand metagermanates of the corresponding metals. Aqueous solutions of germanate react with molybdic and tungstic acids forming heteropoly acids of varying compositions.