Sulphuric acid autoprotolysis and the theory of dissociated solvents

Abstract

If the species in 100 % H₂SO₄ are principally H₂SO₄, H₃O⁺, HSO^–₄, H₃SO⁺₄, HS₂O^–₇, and H₂S₂O₇, the second derivatives of the freezing-point curves (at the pure solvent) for the solutes water and the metal hydrogen sulphates can, in principle, be combined with the first derivatives of H₀ against molality plots to determine all the species concentrations within a consistent dissociation scheme. Though existing H₀ data are not sufficiently precise for a complete test, the cryoscopic results (adapted to temperatures other than the freezing-point by partial enthalpy corrections) point to an extent of antoprotolysis appreciably larger than the currently accepted estimates, but similar in magnitude to the values derived by Hammett and Brand from the trend of acidity function data. If substantiated, such an extent of autoprotolysis may simplify conductance theory in this solvent by eliminating the necessity for an “asymmetric dissociation” contribution.