Nomenclature
CAS number: 7440-66-6
Description and references
Zn; at. wt 65.409; at. no. 30; valence 2.
Group IIB (12). Essential nutritional trace element necessary for
function of many metallogenzymes. Abundance in earth's crust: 0.02%
by wt. Natural isotopes: 64 (48.89%); 66 (27.81%); 68 (18.57%);
67 (4.11%); 70 (0.62%); eight radioactive isotopes and two isomers.
Occurs in smithsonite or zinc spar, sphalerite or zinc blende, zincite,
willemite, franklinite, [(Zn,Mn,Fe)O.(Fe.Mn2)O3] or gahnite (ZnAl2O4). Has been known since
very early times. Commercial forms: ingots; lumps; sheets; wire;
shot; strips; sticks; granules; mossy; powder (dust). Prepn: Gowland,
Bannister, Metallurgy of Non-Ferrous Metals (Griffin, London, 1930); Zinc Production,
Properties and Uses (Zinc Development Association, London,
1968). Reviews: Zinc, C.
H. Mathewson, Ed., A.C.S. Monograph Series no. 142 (Reinhold, New York, 1959) 721 pp; Schlechter, Thompson, “Zinc
and Zinc Alloys” in Kirk-Othmer Encyclopedia
of Chemical Technology vol. 22 (Interscience,
New York, 2nd ed., 1970) pp 555-603; Aylett, “Group IIB” in Comprehensive Inorganic Chemistry vol.
3, J. C. Bailar, Jr. et al., Eds. (Pergamon Press,
Oxford, 1973) pp 187-328. Review of toxicology and human exposure:
Toxicological Profile for Zinc (PB2006-100008, 2005) 352 pp.
Properties
Bluish-white, lustrous metal; distorted hexagonal
close-packed structure; stable in dry air; becomes covered with a
white coating of basic carbonate on exposure to moist air. mp 419.5°. bp 908°. d25 7.14. Heat capacity at constant pressure
(25°): 6.07 cal/mole deg. Mohs' hardness 2.5. When heated to 100-150°
becomes malleable, at 210° becomes brittle and pulverizable. Burns
in air with a bluish-green flame. Loses electrons in aqueous systems
to form Zn2+ E° (aq) Zn/Zn2+ 0.763 V. Slowly
attacked by H2SO4 or HCl; oxidizing agents or
metal ions, e.g. Cu2+, Ni2+, Co2+, accelerate the process. Reacts slowly with ammonia water and acetic
acid; rapidly with HNO3. Reacts with alkali hydroxides
to form “zincates”, ZnO22, which are actually hydroxo
complexes such as Zn(OH)3; Zn(OH)42, [Zn(OH)4(H2O)2]2.Caution
Potential symptoms of overexposure
by fume inhalation are metal fume fever; by acute oral overexposure
are stomach cramps, nausea, vomiting; by chronic oral overexposure
are anemia, pancreatic damage, decreased HDL cholesterol levels (PB2006-100008).Use
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; manuf 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.