Zinc (BioDeep_00000837544)

描述信息

D018977 - Micronutrients > D014131 - Trace Elements
Although zinc is an essential requirement for good health, excess zinc can be harmful. Excessive absorption of zinc suppresses copper and iron absorption. The free zinc ion in solution is highly toxic to plants, invertebrates, and even vertebrate fish. The Free Ion Activity Model is well-established in the literature, and shows that just micromolar amounts of the free ion kills some organisms. A recent example showed 6 micromolar killing 93\\% of all Daphnia in water.; Binary compounds of zinc are known for most of the metalloids and all the nonmetals except the noble gases. The oxide ZnO is a white powder that is nearly insoluble in neutral aqueous solutions, but is amphoteric, dissolving in both strong basic and acidic solutions. The other chalcogenides (ZnS, ZnSe, and ZnTe) have varied applications in electronics and optics. Pnictogenides (Zn3N2, Zn3P2, Zn3As2 and Zn3Sb2), the peroxide (ZnO2), the hydride (ZnH2), and the carbide (ZnC2) are also known. Of the four halides, ZnF2 has the most ionic character, whereas the others (ZnCl2, ZnBr2, and ZnI2) have relatively low melting points and are considered to have more covalent character.; Brass, which is an alloy of copper and zinc, has been used since at least the 10th century BC. Impure zinc metal was not produced in large scale until the 13th century in India, while the metal was unknown to Europe until the end of the 16th century. Alchemists burned zinc in air to form what they called "philosophers wool" or "white snow". The element was probably named by the alchemist Paracelsus after the German word Zinke. German chemist Andreas Sigismund Marggraf is normally given credit for discovering pure metallic zinc in 1746. Work by Luigi Galvani and Alessandro Volta uncovered the electrochemical properties of zinc by 1800. Corrosion-resistant zinc plating of steel (hot-dip galvanizing) is the major application for zinc. Other applications are in batteries and alloys, such as brass. A variety of zinc compounds are commonly used, such as zinc carbonate and zinc gluconate (as dietary supplements), zinc chloride (in deodorants), zinc pyrithione (anti-dandruff shampoos), zinc sulfide (in luminescent paints), and zinc methyl or zinc diethyl in the organic laboratory.; Cadmium zinc telluride (CZT) is a semiconductive alloy that can be divided into an array of small sensing devices. These devices are similar to an integrated circuit and can detect the energy of incoming gamma ray photons. When placed behind an absorbing mask, the CZT sensor array can also be used to determine the direction of the rays. Zinc is used as the anode or fuel of the zinc-air battery/fuel cell providing the basis of the theorized zinc economy.; Groups at risk for zinc deficiency include the elderly, vegetarians, and those with renal insufficiency. The zinc chelator phytate, found in seeds and cereal bran, can contribute to zinc malabsorption in those with heavily vegetarian diets. There is a paucity of adequate zinc biomarkers, and the most widely used indicator, plasma zinc, has poor sensitivity and specificity. Diagnosing zinc deficiency is a persistent challenge.; In weak basic solutions containing Zn2+ ions, the hydroxide Zn(OH)2 forms as a white precipitate. In stronger alkaline solutions, this hydroxide is dissolved to form zincates ([Zn(OH)4]2?). The nitrate Zn(NO3)2, chlorate Zn(ClO3)2, sulfate ZnSO4, phosphate Zn3(PO4)2, molybdate ZnMoO4, cyanide Zn(CN)2, arsenite Zn(AsO2)2, arsenate Zn(AsO4)2?8H2O and the chromate ZnCrO4 (one of the few colored zinc compounds) are a few examples of other common inorganic compounds of zinc. One of the simplest examples of an organic compound of zinc is the acetate (Zn(O2CCH3)2).; Organozinc compounds are those that contain zinc?carbon covalent bonds. Diethylzinc ((C2H5)2Zn) is a reagent in synthetic chemistry. It was first reported in 1848 from the reaction of zinc and ethyl iodide, and was the first compound known to contain a metal?carbon sigma bond. Decamethyldizincocen...

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