Nomenclature
CAS number: 7440-06-4
Description and references
Pt; at. wt 195.084; at. no. 78; valences 2,4;
seldom 1, 5, 6. Group VIII (10). Six naturally occurring isotopes:
190 (0.01%); 192 (0.8%); 194 (32.9%); 195 (33.8%); 196 (25.2%); 198
(7.2%); 190 is radioactive: T 1/2 6.9 × 1011 years.
Artificial, radioactive isotopes: 173-189; 191; 193; 197; 199-201.
Abundance in earth's crust about 0.01 ppm. Believed to be mentioned
by Pliny under the name “alutiae”. Has been known and used in South America as “platina
del Pinto”. Reported by Ulloa in 1735; brought to Europe by Wood,
and described by Watson in 1741. Occurs native alloyed with one or
more members of its group (iridium, osmium, palladium, rhodium, and
ruthenium) in gravels and sands. Prepn: Wichers et al., Trans. Am. Inst. Min. Metall. Eng. 76, 602 (1928). Reviews of prepn, properties and chemistry
of platinum and other platinum metals: Gilchrist, Chem. Rev. 32, 277-372 (1943);
Beamish et al., in Rare Metals
Handbook, C. A. Hampel, Ed. (Reinhold, New York, 1956)
pp 291-328; Livingstone in Comprehensive Inorganic
Chemistry Vol. 3, J. C. Bailar, Jr. et
al., Eds. (Pergamon Press, Oxford, 1973) pp 1163-1189, 1330-1370;
F. R. Hartley, The Chemistry of Platinum and
Palladium with Particular Reference to Complexes of the Elements (Halsted Press, New York, 1973).
Properties
Silver-gray, lustrous, malleable and ductile metal;
face-centered cubic structure. Also prepd in the form of a black
powder (platinum black) and as spongy masses (platinum sponge). mp 1773.5 ± 1°; Roeser et al., Natl. Bur. Stand. J. Res. 6, 1119 (1931); bp about 3827°. d 21.447 (calcd). Brinell hardness: 55. Sp heat 0.0314
cal/g at 0°. Electrical resistivity (20°) 10.6 μohm-cm. Does not
tarnish on exposure to air. Absorbs hydrogen at a red heat and retains
it tenaciously at ord. temp, gives off the gas at a red heat in vacuo. Occludes carbon monoxide, carbon dioxide, nitrogen.
Volatilizes considerably when heated in air at 1500°. The heated
metal absorbs oxygen; gives it off on cooling. Not affected by water
or by single mineral acids. Reacts with boiling aqua regia with formation
of chloroplatinic acid, also with molten alkali cyanides. Attacked
by halogens, by fusion with caustic alkalies, alkali nitrates, alkali
peroxides; by arsenates and phosphates in presence of reducing agents.Caution
Potential symptoms of overexposure
to Pt metal are irritation of eyes, skin, respiratory system; dermatitis.
Potential symptoms of overexposure to soluble Pt salts are irritation
of eyes, nose; cough, dyspnea, wheezing, cyanosis; dermatitis, skin
sensitization; lymphocytosis. See NIOSH Pocket Guide to Chemical Hazards (DHHS/NIOSH 97-140,
1997) p 260. See also E. Browning, Toxicity of Industrial Metals (Appleton-Century-Crofts,
New York, 2nd ed., 1969) pp 270-275.Use
Manuf apparatus for laboratory and industrial use,
thermocouples, platinum resistance thermometers, acidproof containers,
electrodes, etc. In dentistry; jewelry; electroplating. As oxidation
catalyst in manuf acetic acid, nitric acid from ammonia, manuf sulfuric
acid; control of automotive emissions.