Nomenclature
CAS number: 7440-39-3
Description and references
Ba; at. wt. 137.327; at. no. 56; valence 2.
Group IIA (2). Alkaline earth metal. Abundance in earth's crust
0.05% by wt. Naturally occurring isotopes: 138 (71.70%); 137 (11.23%);
136 (7.85%); 135 (6.593%); 134 (2.42%); 132 (0.101%); 130 (0.106%).
Known radioactive isotopes: 117, 119-129, 131, 133, 139-149. Does
not occur free in nature as metal. Compds occur in minerals barite
and witherite. Commercial production by thermal reduction of barium
oxide with aluminum. First prepared as a mercury amalgam by Davy
in 1808. Toxicity studies of barium compds: Syed, Hosain, Toxicol. Appl. Pharmacol. 22, 150
(1972). Reviews: Gmelins, Barium (8th ed.) 30, (1960); Goodenough, Stenger, “Magnesium,
Calcium, Strontium, Barium and Radium” in Comprehensive Inorganic Chemistry Vol. 1, J.
C. Bailar, Jr. et al., Eds. (Pergamon Press, Oxford, 1973)
pp 591-664; Chemistry of the Elements, N. N. Greenwood, A. Earnshaw, Eds. (Pergamon Press, New York, 1984)
pp 117-154; C. Boffito in Kirk-Othmer Encyclopedia
of Chemical Technology vol. 3 (Wiley-Interscience,
New York, 4th ed., 1992) pp 902-908. Review of toxicology and human
exposure: Toxicological Profile for Barium
and Compounds (PB93-110658, 1992) 163 pp.
Properties
Silvery-white, slightly lustrous metal when pure;
yellowish-white when contaminated with nitrogen. Body-centered cubic
structure at atm pressure. Soft, ductile. Fairly volatile; extremely
reactive, very easily oxidizable; must be kept under petroleum or
other oxygen-free liquid to exclude air. Reacts vigorously with water,
liberating hydrogen and creating an explosion hazard. Keep dry and
tightly sealed. Pyrophoric when finely divided; store powder under
dry argon or helium. d 3.6. mp ≈710°.
bp ≈1600°. E0 (aq) Ba2+/Ba 2.91 V. Emits characteristic yellow-green
color in flame. Dissolves in liq NH3 to give deep blue-black
solns. Solns of sol barium salts give a white ppt with H2SO4 or sol sulfates.Caution
Potential symptoms of overexposure
to soluble barium compounds are excessive salivation, vomiting, colic,
diarrhea, convulsive tremors, slow, hard pulse, elevated blood pressure,
confusion; hemorrhages in stomach, intestines, kidneys; respiratory
failure, cardiac arrest. See: Clinical Toxicology of Commercial Products, R. E. Gosselin et al., Eds. (Williams & Wilkins, Baltimore, 5th ed., 1984)
Section III, pp 61-63; Patty's Industrial
Hygiene and Toxicology vol. 2C, G. D. Clayton,
F. E. Clayton, Eds. (Wiley-Interscience, New York, 4th ed., 1994)
pp 1925-1930.Use
Alloys with Al or Mg as “getters” to remove residual
gases from vacuum systems and electronic tubes. Deoxidizer for steel
and other metals. Carrier for radium. The β- and γ-radiation emitted
by
140Ba +
140La makes a large contribution
to the activity of the fission products of uranium rods during the
first few weeks after their withdrawal from the reactor. The emissions
from
133Ba and
137mBa as standards in γ-spectrometry:
Haissinsky, Adloff,
Radiochemical Survey
of the Elements (Elsevier, 1965) pp 12-14.