Hydrogen iodide reducing agent

It is believed that the red phosphorus is the true reducing agent and the iodine (or iodide) functions as a hydrogen carrier. This proc ure replaces the obsolete method of heating with red phosphorus and concentrated hydriodic acid in a sealed tube. 

Phosphonic acid and hydrogen phosphonates are used as strong but slow-acting reducing agents. They cause precipitation of heavy metals from solutions of their salts and reduce sulfur dioxide to sulfur, and iodine to iodide in neutral or alkaline solution. 

Various reducing agents, eg, hydrogen iodide, can abstract chlorine from sulfur monochloride leaving elemental sulfur ... 

Hydrogen iodide is the strongest reducing agent. This trend is expected when the bond enthalpies of the hydrogen halides are considered. 

HYDRIODIC. Clear, or pale yellow liquid, which is an aqueous solution of hydrogen iodide. Hydriodic acid is strong, and an active reducing agent, highly corrosive. 

Hydrogen iodide is used to prepare a number of organic iodides. Hydriodic acid is a reducing agent and is used in the preparation of inorganic iodide salts. It also is used in pharmaceuticals disinfectants, and as a reagent in chemical analysis. 

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