Uses
Germanium oxide 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.
Preparation
Germanium oxide 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.
Reactions
Germanium oxide 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.
Description
Germanium oxide also called Germanium dioxide is the oxide of germanium, an inorganic compound, featuring the chemical formula
GeO
2. It is formed as a passivation layer on pure germanium after exposure to oxygen. Germanium dioxide
generally has a low toxicity, but shows severe nephrotoxicity at higher doses. Germanium dioxide is still
offered on the market in some questionable miracle therapies. Exposure to high doses of germanium dioxide
can lead to germanium poisoning.
Chemical Properties
White powder, hexagonal, tetragonal,
and amorphous.
Uses
Germanium oxide can be used in Phosphors, transistors and diodes, infraredtransmitting glass.
Uses
When Germanium dioxide is 99.999% pure, it is used as a semiconductor in transistors,
in diodes, and to make special infrared transmitting glass.
Uses
Germanium dioxide is used as an optical material for wide-angle lenses and in optical microscope objective lenses. It is used as a catalyst in the preparation of polyethylene terephthalate resin. Further, it is used as a feedstock for the manufacturing of phosphors and semiconductor materials. It is also used in transistors and diodes, and infrared transmitting glass.
Flammability and Explosibility
Not classified
Safety Profile
Poison by
intraperitoneal route. When heated to
decomposition it emits acrid smoke and
irritating fumes.
Purification Methods
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.]
Structure and conformation
Germanium oxide ccurs in two crystalline and one amorphous modifications: (1) a tetragonal rutile form, refractive index 2.05, density 6.24 g/cm3 at 20°C. (2) white hexagonal quartz modification, refractive index 1.735, density 4.70 g/cm3 at 18°C, and (3) a glassy amorphous form, refractive index 1.607, density 3.64 g/cm3 at 20°C. The tetragonal form is practically insoluble in water, while the hexagonal and the amorphous modifications have low solubilities; 0.45 and 0.52% respectively, at 25°C. Aqueous solutions are acidic due to formation of metagermanic acid, H2GeO3. Hexagonal modification converts to a tetragonal crystal system when heated at 350°C in water under pressure. Both crystalline forms convert to a glass-like amorphous GeO2 when heated at 1,100°C.
