Hydrogen Iodide
Structural Formula Vector Image
Title: Hydrogen Iodide
CAS Registry Number: 10034-85-2
CAS Name: Anhydrous hydriodic acid
Molecular Formula: HI
Molecular Weight: 127.91
Percent Composition: H 0.79%, I 99.21%
Literature References: Prepd by catalytic union of the elements: Caley, Burford, Inorg. Synth. 1, 159 (1939); Powell, Campbell, J. Am. Chem. Soc. 69, 1227 (1947). May also be prepd by treating concd hydriodic acid solns with P2O5: Schmeisser in Handbook of Preparative Inorganic Chemistry vol. 1, G. Brauer, Ed. (Academic Press, New York, 2nd ed., 1963) pp 286-289. Lab prepn: Hoffman, Inorg. Synth. 7, 180 (1963). Purification: A. Klemenc, Die Behandlung und Reindarstellung von Gasen (Vienna, 2nd ed., 1948) p 239; Irving, Wilson, Chem. Ind. (London) 1964, 653. Reviews of prepn and properties of HI and other hydrogen halides: Hills in Mellor's vol. II, suppl. 1 (originally published as suppl. II, part 1) 857-869 (1956); Downs, Adams, in Comprehensive Inorganic Chemistry vol. 2, J. C. Bailar, Jr. et al., Eds. (Pergamon Press, Oxford, 1973) pp 1280-1329.
Properties: Colorless, acrid, non-flammable gas. Fumes in moist air. Decomposed by light. mp -50.8°. bp760 -35.1°; bp2 atm -18.9°; bp5 atm 7.3°; bp10 atm 32.0°; bp60 atm 127.5°. d0 5.66; d25 5.23 g/l. Crit temp 151.0°, crit press. 82.0 atm. Sp heat (25°) 0.0545 cal/g/°C. Extremely sol in water. Soly (g/100 g H2O): 234 (10°); 900 (0°). Soly in organic solvents: Gerrard, Chem. Ind. (London) 1969, 295; Ahmed et al., J. Appl. Chem. 20, 109 (1970). Forms an azeotrope with water, see Hydriodic Acid. Reacts with the lower aliphatic alcohols forming the corresponding iodo compds. Forms a colorless liquid at atm pressure when cooled with dry ice and ether or similar cooling mixture. Attacks natural rubber.
Melting point: mp -50.8°
Boiling point: bp760 -35.1°; bp2 atm -18.9°; bp5 atm 7.3°; bp10 atm 32.0°; bp60 atm 127.5°
Density: d0 5.66; d25 5.23 g/l
CAUTION: Strong irritant.
Use: Manuf of hydriodic acid, organic iodo compds, to remove iodine from iodo compds.

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