Second ionization constant of sulfuric acid in H 2 O and D 2 O from 150 to 300 °C at p = 11.5 MPa using flow AC conductivity.

A custom-built flow-through AC conductivity instrument was used to measure the deuterium isotope effect on the ionization quotient of bisulfate from 150 to 300 °C, at p = 11.5 MPa. Standardized solutions of KCl, HCl, KOH, KHSO 4 , K 2 SO 4 , and H 2 SO 4 were prepared in light and heavy waters and their conductivities were measured and fitted with the Quint-Viallard conductivity model to obtain single ion conductivities at infinite dilution for K + , Cl - , H + , OH - , HSO 4 - , and SO 4 2- . These are the first conductivities of DSO 4 - and SO 4 2- measured in heavy water at any temperature, and the first ionization constants for bisulfate reported in heavy water above 225 °C. The deuterium isotope effect on the chemical equilibrium constant, Δp K 2a = p K 2a,D - p K 2a,H , was found to increase with temperature, in contrast to the behaviour seen for other simple oxyacids.