Sodium amalgam or zinc and hydrochloric acid reduce it to lactic acid, whilst hydriodic acid gives propionic acid.
Boron and iodine do not combine directly, but gaseous hydriodic acid reacts with amorphous boron to form the iodide, BI 31 which can also be obtained by passing boron chloride and hydriodic acid through a red-hot porcelain tube.
They are not decomposed by boiling alkalis, but on heating with hydriodic acid they split into their components.
Thus by transposition we may write the last equation as follows 2HI =H2+12+12200 cal., and thus express that hydriodic acid when decomposed into its elements evolves 12200 cal.
Thus, in the production of hydrochloric acid from hydrogen and chlorine 22,000 calories are developed; in the production of hydrobromic acid from hydrogen and bromine, however, only 8440 caloriesare developed; and in the formation of hydriodic acid from hydrogen and iodine 6040 calories are absorbed.
