The molal dissociation quotients and corresponding thermodynamic quantities for water were determined from potentiometric measurements at 25°C intervals from 25 to 250°C in the presence of sodium trifluoromethanesulfonate at six molalities ranging from 0.2 to 6.5. These quantities are compared with published results for the dissociation of water in sodium chloride solutions and an estimate is made of the ion-pair association quotient for HCl.