Conductance of Dilute LiCl, NaCl, NaBr, and CsBr Solutions in Supercritical Water Using a Flow Conductance Cell

Abstract

Conductivities of LiCl(aq), NaCl(aq), NaBr(aq), and CsBr(aq) solutions have been measured in the range of concentrations from 0.013 to 4 × 10-8 mol·dm-3 using a flow conductance cell at temperatures between 603 K and 674 K and pressures between 15 MPa and 28 MPa (water densities from 650 to 200 kg·m-3). Limiting equivalent conductances and ionization equilibrium constants calculated from the concentration dependence of the equivalent conductance are reported. Previous measurements of equilibrium constants in the low-density supercritical region, although of lesser accuracy, agree well with the present results. Even at the critical density and 2.5 K above the critical temperature there is no evidence for the critical effects which make the Debye−Huckel limiting law invalid at the critical isotherm−isobar. No critical scaling of Λ0 is observed. Walden's rule is not obeyed and the Stokes radius increases by 70% near the critical region as the density goes from 700 to 200 kg·m-3, suggesting an increase in the...