Germanium, Tin, and Copper

AbstractGermanium is a semiconducting metal from Group IVA of the periodic table.The physical and chemical properties of germanium and some of its compounds are listed.In 1886 Clemens A. Winkler, a German chemist, isolated germanium from the mineral argyrodite, a mixed sulfide of silver and germanium. It was named after the country of the discoverer. In recent years various germanium compounds, for example, carboxyethyl germanium sesquoxide (Ge‐132) and lactate–citrate–germanate, have been sold as nutritional supplements, thereby increasing exposure above predicted levels.Germanium metal has the most unusual property of being highly transparent to infrared light. This characteristic, coupled with a high index of refraction, is used to advantage in making unique optical elements. Crystalline germanium is a true semiconductor; traces of impurities of 0.1 ppm such as antimony, tin, and lead will lower its electric resistivity from 50 to 0.1–10 ohm/cm. Germanium forms alloys with many metals, producing solid solutions or intermetallic compounds that expand on solidification. Germanium forms a series of hydrides, germanes. They possess pungent odors, are combustible, and are often explosive. Germanium tetrahydride, GeH4, does not react with O2below 230°C or explode below 330°C; digermane (Ge2H6) is more explosive. A series of halogenated germanes are known that are colorless gases or liquids. Although germanium does not form a carbide, it forms strong bonds with carbon atoms to form a variety of organo compounds such as tetraalkyl‐ and tetraarylgermanes. They are volatile, stable, colorless substances, insoluble in water, but soluble in organic solvents.Germanium forms a series of hydrides that correspond chemically to the methane series of hydrocarbons and to silanes (silicon series of hydrides).There are numerous organogermanium compounds. Interest in the organogermanium compounds has centered around their antimicrobial activity and the fact that their mammalian toxicity is considerably lower than the corresponding derivatives of tin or lead.Tin has played a major role in the development of civilization. The Bronze Age began approximately 3500B.C.with the discovery that easily smelted soft copper could be made harder and stronger by alloying with tin. The first inclusion of tin in bronze was probably an accidental result of tin ore being found in copper ore; pure tin was most likely obtained at a later date.The physical and chemical properties of tin and some of its compounds are listed. Data are given for elemental tin, organocompounds and morgonic tin. There is a vast difference between morganic and organic compounds.Copper is one of the metals to which workers have a great deal of occupational exposure. It is estimated that 46,481 workers are exposed to copper on a full‐time basis. Of 12,035 combined federal and state OSHA samples, 7.8% were above the PEL, and 15% were above half of the PEL. The adverse health effects associated with copper production may be due to the large amounts of sulfur oxides generated or because of the impurities, such as arsenic and antimony, which are associated with the copper ores.The Agency for Toxic Substances and Disease Research estimated that the concentration of copper in air ranges from 1 to 200 ng/m3. The average concentration in drinking water ranges from 20 to 75 ppb, although morning concentrations may reach 1 ppm due to water standing overnight in copper pipes and brass faucets. Uncontaminated soil may contain between 2 and 250 ppm of copper, although soil concentrations may reach nearly 7000 ppm in the vicinity of copper production facilities. The average daily dietary intake (water and food) is approximately 1 mg/d. Copper is essential to health and longevity in humans.