Germanium is a chemical element. The chemical symbol of germanium is Ge. The atomic number of germanium is 32. In the periodic table of the chemical elements in the fourth period, IVA group. Germanium elemental is a kind of gray classes, metal luster, qualitative hard, belong to the carbon group, chemical properties and kin tin similar to silicon, insoluble in water, hydrochloric acid, dilute caustic solution, soluble in aqua regia, concentrated nitric acid or sulfuric acid, with both sexes, therefore, soluble in the molten alkali, alkaline peroxide, alkali metal nitrate or carbonate, relatively stable in the air, in nature, a total of five germanium isotope: 70,72,73,74,76, above 700 ℃ and oxygen generated GeO2 and above 1000 ℃, with hydrogen powder germanium can burn in the presence of chlorine or bromine, germanium is excellent semiconductor, as a high frequency current detection and rectifier with alternating current (ac), in addition, can be used in the infrared materials, precision instruments, the catalyst. Compounds of germanium can be used to make fluorescent plates and various kinds of glass with high refractive index.