3D model (JSmol)
|Molar mass||127.91 g/mol|
|Density||1.70 g/mL, azeotrope|
(57% HI by weight)
|Boiling point||127 °C (261 °F; 400 K) 1.03 bar, azeotrope|
|P260, P264, P280, P301+P330+P331, P303+P361+P353, P304+P340, P305+P351+P338, P310, P321, P363, P405, P501|
|NFPA 704 (fire diamond)|
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
Hydroiodic acid (or hydriodic acid) is an aqueous solution of hydrogen iodide (HI). It is a strong acid, one that is ionized completely in an aqueous solution. It is colorless. Concentrated solutions are usually 48% to 57% HI.
Hydroiodic acid reacts with oxygen in air to give iodine:
Like other hydrogen halides, hydroiodic acid adds to alkenes to give alkyl iodides. It can also be used as a reducing agent, for example in the reduction of aromatic nitro compounds to anilines.
The Cativa process is a major end use of hydroiodic acid, which serves as a co-catalyst for the production of acetic acid by the carbonylation of methanol.
Hydroiodic acid is listed as a U.S. Federal DEA List I Chemical, owing to its use as a reducing agent related to the production of methamphetamine from ephedrine or pseudoephedrine (recovered from nasal decongestant pills).