Chloric acid

Chloric acid, HClO3, is an oxoacid of chlorine, and the formal precursor of chlorate salts. It is a strong acid (pKa ≈ −2.7 (***note: pKa not in agreement with properties in chem box at right)) and an oxidizing agent.

Chloric acid
Other names
Chloric(V) acid
3D model (JSmol)
ECHA InfoCard 100.029.303
EC Number
  • 232-233-0
UN number 2626
  • InChI=1/ClHO3/c2-1(3)4/h(H,2,3,4)
  • O[Cl+2]([O-])[O-]
Molar mass 84.45914 g mol−1
Appearance colourless solution
Density 1 g/mL, solution (approximate)
>40 g/100 ml (20 °C)
Acidity (pKa) ~ −1
Conjugate base Chlorate
Occupational safety and health (OHS/OSH):
Main hazards
Oxidant, Corrosive
GHS labelling:
H271, H314
P210, P220, P221, P260, P264, P280, P283, P301+P330+P331, P303+P361+P353, P304+P340, P305+P351+P338, P306+P360, P310, P321, P363, P370+P378, P371+P380+P375, P405, P501
NFPA 704 (fire diamond)
Related compounds
Other anions
bromic acid
iodic acid
Other cations
ammonium chlorate
sodium chlorate
potassium chlorate
Related compounds
hydrochloric acid
hypochlorous acid
chlorous acid
perchloric acid
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
Infobox references


Chloric acid is thermodynamically unstable with respect to disproportionation.

Chloric acid is stable in cold aqueous solution up to a concentration of approximately 30%, and solution of up to 40% can be prepared by careful evaporation under reduced pressure. Above these concentrations, chloric acid solutions decompose to give a variety of products, for example:

8 HClO3 → 4 HClO4 + 2 H2O + 2 Cl2 + 3 O2
3 HClO3 → HClO4 + H2O + 2 ClO2


Chloric acid is a powerful oxidizing agent. Most organics and flammables will deflagrate on contact.


It can be prepared by the reaction of sulfuric acid with barium chlorate, the insoluble barium sulfate being removed by precipitation:

Ba(ClO3)2 + H2SO4 → 2 HClO3 + BaSO4

Another method is the heating of hypochlorous acid, producing chloric acid and hydrogen chloride:

3 HClO → HClO3 + 2 HCl

See also


    • Greenwood, Norman N.; Earnshaw, Alan (1997). Chemistry of the Elements (2nd ed.). Butterworth-Heinemann. ISBN 978-0-08-037941-8.
    • R. Bruce King, ed. (1994). "Chloric acid". Encyclopedia of Inorganic Chemistry. Vol. 2. Chichester: Wiley. p. 658. ISBN 0-471-93620-0.
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