Chloric acid, HClO₃, is an oxoacid of chlorine, and the formal precursor of chlorate salts. It is a strong acid (pK_a ≈ −1) and oxidizing agent.

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

Ba(ClO₃)₂ + H₂SO₄ → 2HClO₃ + BaSO₄

Another method is the heating of hypochlorous acid, of which productions include chloric acid and hydrogen chloride:

3HClO → HClO₃ + 2 HCl

It 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, and on warming, chloric acid solutions decompose to give a variety of products, for example:

8HClO₃ → 4HClO₄ + 2H₂O + 2Cl₂ + 3 O₂

3HClO₃ → HClO₄ + H₂O + 2 ClO₂

The decomposition is controlled by kinetic factors: indeed, chloric acid is never thermodynamically stable with respect to disproportionation.

See also

• Hypochlorous acid
• Chlorous acid
• Perchloric acid
• Bromic acid
• Iodic acid

References

• King, R. B. (Ed.) (1994) Encyclopedia of Inorganic Chemistry, Vol. 2, p. 658. Chichester:Wiley. ISBN 0-471-93620-0