Hypochlorous Acid

Title: Hypochlorous Acid
CAS Registry Number: 7790-92-3
Molecular Formula: ClHO
Molecular Weight: 52.46
Percent Composition: Cl 67.58%, H 1.92%, O 30.50%
Line Formula: HClO
Literature References: Known in aq soln only. Formed by the action of water on chlorine: Cady, Inorg. Synth. 5, 160 (1957). A 25% soln of hypochlorous acid is obtained when chlorine hydrate and mercuric oxide are distilled at low pressure: Goldschmidt, Ber. 52, 753 (1919). Review: J. A. Wojtowicz, "Chlorine Monoxide, Hypochlorous Acid, and Hypochlorites", in Kirk-Othmer Encyclopedia of Chemical Technology vol. 5 (Wiley-Interscience, New York, 3rd ed., 1979) pp 580-611.
Properties: Aq soln (25%), greenish yellow liquid. May be stored for a few days if kept at -20°. Dec slowly to Cl2, O2 and HClO4. Very weak acid. pK (25°) 7.49. Strong oxidizing agent. When a 25% soln is evapd in a vacuum, chlorine monoxide, Cl2O, is given off. Cl2O in soln with HClO may be removed by shaking with carbon tetrachloride, but will form again. Protect from light.
pKa: pK (25°) 7.49
NOTE: An aqueous soln of the potassium salt is known as Javelle water or Eau de Javelle (also used for sodium hypochlorite, q.v.).
Use: Disinfectant.
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