Hydriodic acid forms when hydrogen iodide -- a colorless gas with a sharp odor -- is dissolved in water. This pale yellow water solution is a strong, highly corrosive acid and a powerful reducing agent. It has the ability to lose a proton or take it back during chemical reactions. Because of this property, hydriodic acid has found many uses in chemical-based applications.
A catalyst accelerates chemical reactions within another chemical. Hydriodic acid, because of its strong reducing ability and acidity, is commonly used to produce acetic acid. Acetic acid, although toxic to humans in concentrated forms, is the basic chemical that produces vinegar.
Hydriodic acid is also commonly used in both organic and inorganic iodide preparations; however, it is one of the most expensive catalyzing reagents used in this process.
Hydriodic acid's high level of acidity allows it to kill several types of germs and viruses. It is often used to disinfect and sanitize medical tools and products, such as control products used in mastitis, a common bacterial complication experienced by women who breastfeed.
In its syrup form (the acid being highly unstable), it is used as a pharmaceutical intermediate to manufacture various medicines for such conditions as chronic bronchitis, scrofula and malarial infections. Pharmaceutical intermediates are chemicals added to a chemical mixture to make it react and turn into another compound.
Methamphetamine, an illegal and addictive drug also known as "ice" or "meth," can be produced when hydriodic acid is combined with red phosphorus and pseudoephedrine or ephedrine. Hydriodic acid, because of its excellent catalyzing ability, can produce large amounts of the drug without the need for complicated chemical processes.