Hammett acidity function, H₀, of hydrobromic acid and its ionic dissociation

The Hammett acidity function, H₀, of hydrobromic acid was determined at 25.0 and 60°C by means of nitro-and chloro-substituted aniline indicators and compared with similar data for sulfuric acid, obtained concurrently, and for perchloric acid, from the literature. Care was taken to remove traces of bromine from the hydrobromic acid solutions, which otherwise cause difficulties. The data were examined according to the approaches suggested severally by Wyatt, Dawber, and Högfeldt, with the view of obtaining the degree of dissociation α of the hydrobromic acid. It was concluded, however, that the empirical relationships on which these approaches are based are not sufficient to give valid estimates of α for an acid as strong as hydrobromic acid.