Zinc is another earliest known metal. Use of its alloy, brass, dates back to prehistoric times. The metal was produced in India in the 13th century by reducing calamine (a silicate mineral of zinc) with wool. Marggraf produced the metal in 1746 by reducing calamine with charcoal. The element took its name from the German word zink meaning “of obscure origin.” Lohneyes first used this name in 1697. Zinc occurs in nature, widely distributed. The principal ores are sphalerite (and wurtzite) known as zinc blende, ZnS; gahnite, ZnAl2O4; calamine; smithsonite, ZnCO3; franklinite, ZnFe2O4; and zincite, ZnO. Abundance in earth’s crust is about 70 mg/kg and average concentration in sea water is about 10 µg/L.
Some important applications of zinc include galvanizing steel; to produce die castings; as a chemical additive in rubber and paints; in dry cells; in making electrodes; and as a reducing agent. Steel is galvanized by a thin coating of zinc to protect it from corrosion. Such galvanized steel is used in buildings, cars, and appliances. High-purity zinc is alloyed with aluminum at varying compositions, along with small amounts of copper and magnesium, to produce die castings. Such die castings are used extensively in automotive, hardware, and electrical industries. Zinc forms numerous alloys including brass, nickel silver, German silver, commercial bronze, soft solder, aluminum solder, and spring brass. The laboratory use of zinc includes preparating hydrogen gas and as a reducing agent in a number of chemical reactions. Zinc salts have numerous uses (See under specific compounds). Zinc is an essential nutrient element required for growth of animals.
Galvanizing sheet iron; as ingredient of alloys such as bronze, brass, Babbitt metal, German silver, and special alloys for die-casting; as a protective coating for other metals to prevent corrosion; for electrical apparatus, especially dry cell batteries, household utensils, castings, printing plates, building materials, railroad car linings, automotive equipment; as reducing agent in organic chemistry; for deoxidizing bronze; extracting gold by the cyanide process, purifying fats for soaps; bleaching bone glue; manufacture of sodium hydrosulfite; insulin zinc salts; as reagent in analytical chemistry, e.g., in the Marsh and Gutzeit test for arsenic; as a reducer in the determination of iron. It is a nutritional trace element.
Inhalation or contact with vapors, substance or decomposition products may cause severe injury or death. May produce corrosive solutions on contact with water. Fire will produce irritating, corrosive and/or toxic gases. Runoff from fire control may cause pollution.
Produce flammable gases on contact with water. May ignite on contact with water or moist air. Some react vigorously or explosively on contact with water. May be ignited by heat, sparks or flames. May re-ignite after fire is extinguished. Some are transported in highly flammable liquids. Runoff may create fire or explosion hazard.
silver or blueish-white foil or powder
Bluish-white lustrous metal; brittle at room temperature; malleable between 100 to 150°C; hexagonal close-packed structure; density 7.14 g/cm3; melts at 419.6°C; vaporizes at 907°C; vapor pressure 1 torr at 487°C, 5 torr at 558°C and 60 torr at 700°C; good conductor of electricity, electrical resistivity 5.46 microhm-cm at 0°C and 6.01 microhm-cm at 25°C; surface tension 768 dynes/cm at 600°C; viscosity 3.17 and 2.24 centipoise at 450 and 600°C, respectively; diamagnetic; magnetic susceptibility 0.139x10–6 cgs units in polycrystalline form; thermal neutron absorption cross-section 1.1 barns.
ZINC METAL is a reducing agent. Reacts violently with oxidants causing fire and explosion hazards [Handling Chemicals Safely 1980. p. 966]. In the presence of carbon, the combination of chlorine trifluoride with zinc results in a violent reaction [Mellor 2, Supp. 1: 1956]. Sodium peroxide oxidizes zinc with incandescence [Mellor 2:490-93 1946-47]. Zinc powder or dust in contact with acids forms hydrogen. The heat generated by the reaction is sufficient to ignite the hydrogen evolved [Lab. Govt. Chemist 1965]. A mixture of powdered zinc and an oxidizing agent such as potassium chlorate or powdered sulfur can be exploded by percussion. Zinc burns in moist chlorine. A mixture of zinc and carbon disulfide reacts with incandescence. Zinc powder reacts explosively when heated with manganese chloride. The reaction between zinc and selenium or tellurium is accompanied by incandescence [Mellor 4:476-480 1946-47]. When zinc and ammonium nitrate are mixed and wetted with a minimum of water, a violent reaction occurs with evolution of steam and zinc oxide. When hydrazine mononitrate is heated in contact with zinc a flaming decomposition occurs at temperatures a little above its melting point. Hydroxylamine is reduced when heated with ZINC, unpredictably ZINC may either ignite and burn or explode [Mellor 8 1946-47].
Commercial zinc dust (1.2kg) is stirred with 2% HCl (3L) for 1minute, then the acid is removed by filtration, and washed in a 4L beaker with a 3L portion of 2% HCl, three 1L portions of distilled water, two 2L portions of 95% EtOH, and finally with 2L of absolute Et2O. (The wash solutions were removed each time by filtration.) The material is then dried thoroughly, and if necessary, any lumps are broken up in a mortar. [Wagenknecht & Juza Handbook of Preparative Inorganic Chemistry (Ed. Brauer) Academic Press Vol II p 1067 1965.]
A grayish powder. Insoluble in water. May produce toxic zinc oxide fumes when heated to very high temperatures or when burned. Used in paints, bleaches and to make other chemicals.
Air & Water Reactions
Can evolve gaseous hydrogen in contact with water or damp air. The heat of the reaction may be sufficient to ignite the hydrogen produced [Haz. Chem. Data 1966. p. 171]. Flammable. May form an explosive mixture with air [Hawley].
Zinc exhibits a valence of +2 in all its compounds. It also is a highly electropositive metal. It replaces less electropositive metals from their aqueous salt solutions or melts. For example, a zinc metal bar put into Cu2+ solution acquires a brown-black crust of copper metal deposited on it. At the same time the blue color of the solution fades. Zinc reduces Cu2+ ions to copper metal. The overall reaction is:
Zn(s) + Cu2+(aq) → Zn2+(aq) + Cu(s)
This spontaneous reaction was used first in 1830 to make a voltaic cell.
The metal is attacked by mineral acids. Reactions with sulfuric and hydrochloric acids produce hydrogen. With nitric acid, no hydrogen is evolved but the pentavalent nitrogen is reduced to nitrogen at lower valence states.
Zinc is attacked by moist air at room temperature. Dry air has no action at ambient temperatures but the metal combines with dry oxygen rapidly above 225°C.
Zinc reacts with carbon dioxide in the presence of moisture at ordinary temperatures forming a hydrated basic carbonate. The metal, on heating with dry halogen gases, yields zinc halides. However, in the presence of moisture the reaction occurs rapidly at ambient temperatures.
The metal dissolves in hot solutions of caustic alkalis to form zincates and evolves hydrogen:
Zn + 2NaOH → Na2ZnO2 + H2