Iodic acid (HIO3): properties, structure, and uses

Structure and key characteristics

As a molecule HIO3 consists of hydrogen bonded to an oxoanion. In aqueous solution it is the conjugate acid of the iodate ion. The compound is typically encountered as a white crystalline solid that is moderately soluble in water. The iodine element involved is discussed further at iodine, and the hydrogen component at hydrogen. The oxidation level is described at +5.

Chemical behaviour

Iodic acid acts as an oxidizing agent and can be converted to iodate salts through neutralization. On dehydration it can yield iodine oxides such as iodine pentoxide (I2O5). In solution the acid–base equilibrium produces iodate ions; salts and derivatives are widely studied in inorganic chemistry. For notes on ionic forms see iodate/ion chemistry.

Preparation and reactions

Laboratory preparation commonly involves oxidizing iodine-containing species or treating iodates under appropriate conditions to obtain HIO3. It participates in redox reactions typical of oxyacids of halogens and is occasionally used as a mild, solid oxidant in synthesis. It can be handled to produce stable iodate compounds for analytical purposes.

Uses, importance and distinctions

• Analytical chemistry: source of iodate for standards and titrations.
• Chemical synthesis: oxidant and precursor to iodate salts.
• Teaching and research: example of a +5 oxidation state oxoacid.

Related iodine oxyacids include iodous acid (HIO2, iodine +3) and periodic acid (HIO4 or H5IO6, iodine +7); these differ in oxidation state and reactivity. Iodic acid should not be confused with its salts (iodates) or with elemental iodine.

Safety and handling

Iodic acid is an oxidizer and should be handled with appropriate precautions: avoid contact with combustible materials, use suitable eye and skin protection, and follow laboratory safety guidelines. For specific safety data consult appropriate material safety resources.