Conductivity Measurements of Dilute Aqueous HCl Solutions to High Temperatures and Pressures Using a Flow-Through Cell

Abstract

The limiting molar conductance Λ0 and molal ion association constant KA(m) of dilute (10-5 to 10-3 mol·kg-1) aqueous HCl solutions were determined using a flow-through conductance cell at temperatures from 100 to 410 °C and densities from 0.96 to 0.27 g·cm-3. The flow-through cell is designed to measure molar conductances of dilute aqueous electrolytes with a high degree of accuracy at high temperatures and low densities. The resulting Λ0 values are in general agreement with those reported by Noyes (1907), Wright et al. (1961), Pearson et al. (1963), and Lukashov et al. (1975) for densities that range from 0.7 to 0.4 g·cm-3 at comparable conditions. However, when compared to values reported by Frantz and Marshall (1984), the new results are in agreement at densities (ρ) > 0.5 g·cm-3, but from 0.5 to ca. 0.4 g·cm-3, their calculated results are 5−11% higher. Below 0.4 g·cm-3 where the experimental uncertainties are large, the weighted values from the new study are approximately 14−35% lower. Within experimental uncertainties, the new KA(m) values are in good agreement with the reported values from Franck (1956), Wright et al. (1961), Pearson et al. (1963), and Lukashov et al. (1975) at densities from 0.7 to 0.3 g·cm-3 but are only in fair agreement with the Frantz and Marshall values at densities above 0.5 g·cm-3. Below 0.5 g·cm-3, the latter values are 0.5−2.5 log units higher than the new results.