germanium (jərmā´nēəm) [from Germany], semimetallic chemical element; symbol Ge; at. no. 32; at. wt. 72.63; m.p. 937.4°C; b.p. 2,830°C; sp. gr. 5.323 at 25°C; valence +2 or +4. Pure germanium is a lustrous, gray-white, brittle metalloid with a diamondlike crystalline structure. It is similar in chemical and physical properties to silicon, below which it appears in Group 14 of the periodic table. Germanium is very important as a semiconductor. Transistors and integrated circuits provide the greatest use of the element; they are often made from germanium to which small amounts of arsenic, gallium, or other metals have been added. Numerous alloys containing germanium have been prepared. Germanium forms many compounds. Germanium oxide is added to glass to increase the index of refraction; such glass is used in wide-angle lenses. Since the oxide is transparent to infrared radiation, it has found use in optical instruments. Germanium tetrachloride is a liquid that boils at 84°C; it is an intermediate in the production of pure germanium. Other halides are known. Germane (germanium tetrahydride) is a gas that decomposes at about 300°C to hydrogen and germanium; it is sometimes used in the production of semiconductor devices. A sulfide and numerous organo-germanium compounds are known. Germanium occurs in a few minerals, e.g., argyrodite (with silver and sulfur), zinc blende (with zinc and sulfur), and tantalite (with iron, manganese, and columbium). The chief ore of germanium is germanite, which contains copper, sulfur, about 7% germanium, and 20 other elements. Germanium is produced as a byproduct of the refining of other metals; there is considerable recovery from flue dusts and from ashes of certain coals with high germanium content. The element was called ekasilicon by D. I. Mendeleev, who predicted its properties with striking accuracy from its position in his periodic table. It was first isolated from argyrodite in 1886 by Clemens Winkler, a German chemist, who gave it the name germanium.