Title: Cobaltous Iodide
CAS Registry Number: 15238-00-3
Synonyms: Cobalt diiodide
Molecular Formula: CoI2
Molecular Weight: 312.74
Percent Composition: Co 18.84%, I 81.16%
Literature References: Prepn: Clark, Buchner,
J. Am. Chem. Soc. 44, 230 (1922); Chaigneau,
Bull. Soc. Chim. Fr. 1957, 886; Chaigneau, Chastagnier,
ibid. 1958, 1192; Glemser in
Handbook of Preparative Inorganic Chemistry vol. 2, G. Brauer, Ed. (Academic Press, New York, 2nd ed., 1965) p 1518.
Properties: The anhydr salt exists in two isomorphous forms. a-CoI2: black, graphite-like solid. mp 515-520° (in high vacuum). d425 5.584. Very hygroscopic, becomes blackish-green in air. Sol in water to give pink to red soln. b-CoI2: ochre-yellow powder. Blackens at 400° and converts to a-form. d425 5.45. Very hygroscopic; deliquesc in moist air forming green droplets. Sol in water to give colorless soln which becomes pink on heating.
Melting point: mp 515-520° (in high vacuum)
Density: d425 5.584; d425 5.45
Derivative Type: Hexahydrate
Properties: Dark red hexagonal prisms. Loses H2O on heating becoming anhydr by 130°. d 2.90. Loses I2 on exposure to air and light. Sol in water to give soln which is red below 20°, olive green at 20 to 40°, and green at higher temps. Sol in ethanol (blue soln), ether (blue to green soln), chloroform (blue soln), acetone.
Density: d 2.90
Use: Indicator for moisture and humidity; determination of water in organic solvents; catalyst for organic reactions.
