Nomenclature
CAS number: 7440-28-0
Description and references
Tl; at. wt 204.3833; at. no. 81; valence 1,
3. Group IIIA(13). Naturally occurring isotopes: 203 (29.50%),
205 (70.50%); artificial, radioactive isotopes: 191-202; 204; 206-210.
Occurs in crookesite, (Cu,Tl,Ag)2Se, found in Sweden;
in lorandite, TlAsS2, found in Greece; in hutchinsonite,
(Tl,Cu,Ag)2S.PbS.2As2S3, found in
Switzerland. Occurrence in the earth's crust: 0.7 ppm. Discovered
by Crookes in 1861. Prepn: Sanderson, Can.
Mining J. 65, 624 (1944). Use in organic syntheses:
McKillop et al., Tetrahedron Lett. 1970, 5281; Taylor et al., ibid. 5285. Review: Wade, Banister in Comprehensive Inorganic Chemistry vol. 1, J.
C. Bailar, Jr. et al., Eds. (Pergamon Press, Oxford, 1973)
pp 997-1000, 1119-1172. Review of toxicity: E. Browning, Toxicity of Industrial Metals (Appleton-Century-Crofts,
New York, 2nd ed., 1969) pp 317-322; of toxicology and human exposure:
Toxicological Profile for Thallium (PB93-110856, 1992) 114 pp.
Properties
Bluish-white, very soft, inelastic, easily fusible,
heavy metal; leaves a streak on paper. Oxidizes superficially in
air forming a coating of Tl2O. Forms alloys with other
metals and readily amalgamates with mercury. d 11.85. Begins to volatilize at 174°. mp 303.5°. bp 1457°. Specific heat at 20° 0.031
cal/g/°C. Latent heat of fusion 5.04 cal/g. Brinell hardness: 2.
May be distilled in a stream of hydrogen. Insol in water; reacts
with nitric or sulfuric acid; difficultly with hydrochloric acid.Caution
Potential symptoms of overexposure
are nausea, diarrhea, abdominal pain and vomiting; ptosis, strabismus;
peripheral neuritis, tremor; retrosternal tightness, chest pain and
pulmonary edema; seizure, chorea and psychosis; liver and kidney damage;
alopecia; paresthesia of legs. See NIOSH Pocket Guide to Chemical Hazards (DHHS/NIOSH 97-140,
1997) p 304. See also Patty's
Industrial Hygiene and Toxicology vol. 2A, G.
D. Clayton, F. E. Clayton, Eds. (Wiley-Interscience, New York, 3rd
ed., 1981) 1914-1931.Use
In semi-conductor industry; alloyed with mercury
for switches and closures which operate at subzero temps. In manuf
of highly refractive optical glass. Has been used in admixture with
97-98% of inert substances as poison for rats and other rodents.