hydriodic

They are not decomposed by boiling alkalis, but on heating with hydriodic acid they split into their components.

When heated with concentrated hydrobromic or hydriodic acids, it is converted into fumaric acid.

Reducing agents (zinc and caustic alkali, hydriodic acid, sodium amalgam, &c.) convert it into succinic acid.

The bromide and iodide are formed in a similar manner by heating the metal in gaseous hydrobromic or hydriodic acids.

Give the formula for the salt which phosphine forms with hydriodic acid.