Gold
Title: Gold
CAS Registry Number: 7440-57-5
Literature References: Au; at. wt 196.966569; at. no. 79; valences 1, 3. Group IB (11). Occurrence in the earth's crust: 0.005 ppm. One natural isotope: 197; artificial isotopes (mass numbers): 177-179, 181, 183, 185-196, 198-203. Probably the first pure metal known to man. Occurs in nature in its native form and in minute quantities in almost all rocks and in seawater. Gold ores include calavarite, (AuTe2), sylvanite, [(Ag,Au)Te2], petzite, [(Ag,Au)2Te]. Methods of mining, extracting and refining: Hull, Stent in Modern Chemical Processes Vol. 5 (Reinhold, New York, 1958) pp 60-71. Lab prepn of gold powder from gold pieces: Block, Inorg. Synth. 4, 15 (1953). Chemistry of gold drugs in the treatment of rheumatoid arthritis: D. H. Brown, W. E. Smith, Chem. Soc. Rev. 9, 217 (1980). Use as catalyst in oxidation of organic compds by NO2: R. E. Sievers, S. A. Nyarady, J. Am. Chem. Soc. 107, 3726 (1985). Least reactive metal at interfaces with gas or liquid: B. Hammer, J. K. Norskov, Nature 376, 238 (1995). Reviews: Gmelins, Gold (8th ed.) 62, parts 2, 3 (1954); Johnson, Davis, "Gold" in Comprehensive Inorganic Chemistry vol. 3, J. C. Bailar Jr. et al., Eds. (Pergamon Press, Oxford, 1973) pp 129-186; J. G. Cohn, E. W. Stern in Kirk-Othmer Encyclopedia of Chemical Technology vol. 11 (Wiley-Interscience, New York, 3rd ed., 1980) pp 972-995.
Properties: Yellow, soft metal; face-centered cubic structure; when prepared by volatilization or precipitation methods, deep violet, purple, or ruby powder, mp 1064.76°; bp 2700°. d 19.3. Hardness (Mohs') 2.5-3.0; (Brinell's) 18.5. Extremely inactive; not attacked by acids, air or oxygen. Superficially attacked by aq halogens at room temp. Reacts with aqua regia, with mixtures contg chlorides, bromides, or iodides if they can generate nascent halogens, with many oxidizing mixtures especially those contg halogens. Also with alkali cyanides, solns of thiocyanates and double cyanides.
Melting point: mp 1064.76°
Boiling point: bp 2700°
Density: d 19.3
Use: In manuf jewelry; in gold plating other metals; as a standard of currency; most frequently alloyed with silver and copper. For use in medicine, see Gold, Radioactive, Colloidal.

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