Hypoiodous acid

Hypoiodous acid is the inorganic compound with the chemical formula HIO. It forms when an aqueous solution of iodine is treated with mercuric or silver salts. It rapidly decomposes by disproportionation:

Hypoiodous acid is a weak acid with a pK_a of about 11. The conjugate base is hypoiodite (IO). Salts of this anion can be prepared by treating I₂ with alkali hydroxides. They rapidly disproportionate to form iodides and iodates.