Hydroiodic acid
Hydroiodic acid (or hydriodic acid) is a colorless liquid. It is an aqueous solution of hydrogen iodide with the chemical formula Template:Chem2. It is a strong acid, in which hydrogen iodide is ionized completely in an aqueous solution. Concentrated aqueous solutions of hydrogen iodide are usually 48% to 57% HI by mass.<ref name=Ullmann>Template:Ullmann</ref>
Preparation
Reactions
Hydroiodic acid reacts with oxygen in air to give iodine:
Like 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.<ref>Template:Cite journal</ref>
Cativa process
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.<ref name = "Cativa">Template:Cite journal</ref><ref>Template:Cite journal</ref>
Illicit uses
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).<ref>Template:Cite journal</ref>