Thread Content
In 1871, Mendeleev predicted the existence of this element, and in 1886, the German C.A. Winkler discovered germanium while analyzing sphalerite. It is an element of group ⅣA in the fourth period, with the symbol Ge. Its total mass content in the Earth’s crust is about 7×10-4%, and minerals with a higher germanium content are very rare. It is found in coal, iron ores, as well as in certain types of silver sand and copper ores; it also exists in the form of germanite, GeO2. Germanium appears dark blue in powder form, while its crystals are silver-white and brittle; it is a rare metal with a structure similar to that of carbon. Germanium is insoluble in water, hydrochloric acid, and dilute alkali solutions, but soluble in aqua regia, concentrated nitric acid or sulfuric acid, molten alkalis, sodium peroxide, nitrates, or carbonates. It does not oxidize in air, and its fine powder can burn in chlorine or liquid bromine. In compounds, it usually exhibits +II and +IV oxidation states, and Ge(IV) compounds are more stable, such as germanium dioxide GeO2 and germanium chloride GeCl4. High-purity germanium is a semiconductor material that can be produced by reducing high-purity germanium oxide followed by melting. Germanium single crystals doped with trace amounts of specific impurities can be used to manufacture various transistors, rectifiers, and other devices; germanium is also used in alloys and welding. Compounds of germanium are used to manufacture fluorescent plates and various glasses with high refractive indices. Germanium can be produced by reducing germanium dioxide with carbon; it can also be recovered from the flue ash of gas generators.