ARSENOUS ACID IONISATION IN AQUEOUS SOLUTIONS FROM 25 TO 300 °C

Abstract

The ultraviolet spectra of dilute, aqueous arsenic (III)-containing solutions have been measured from 25 to 300 °C at the saturated vapour pressure. From these measurements, the equilibrium constant was obtained for the reaction{A formula is presented}for which pK1 (arsenous acid) decreases from 9.25 to 7.11 over a temperature range from 25 to 300 °C. In addition, electrospray mass spectrometric measurements support the conclusion that the arsenous acid moeities in low density aqueous media are HAsO2 and AsO2-.