What is hydrogen triiodide?

Hydrogen triiodide (HI3) is a highly reactive and unstable chemical compound composed of one atom of hydrogen and three atoms of iodine. It is a reddish-brown liquid that is highly soluble in water. HI3 is one of the strongest known acids, with a pKa of about -11, making it even stronger than sulfuric acid. It is also highly reactive and can easily decompose into hydrogen and iodine under normal conditions. As a result of its instability, it is not commonly used in industrial or laboratory applications. However, it has been used in the past as a reagent in organic chemistry, particularly in the production of alkyl iodides.