Nomenclature
CAS number: 15238-00-3
Cobalt diiodide.
CoI
2; mol wt 312.74.
Co 18.84%, I 81.16%.
Description and 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.
α-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. β-CoI2: ochre-yellow powder.
Blackens at 400° and converts to α-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.Derivative
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.Use
Indicator for moisture and humidity; determination
of water in organic solvents; catalyst for organic reactions.