The limiting molar conductance Λ 0 and molal ion association constant K A (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 Λ 0 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 (F) > 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 K A (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.

The limiting molar conductance (Λ0) and molal ion association constant (K A(m)) of dilute (10-5 to 10-3 mol kg-1) aqueous LiOH, NaOH, and KOH solutions were determined by a flow-through conductance cell from 50 to 410 °C and pressures up to 33 MPa. The flow-through cell is designed to measure molar conductances of dilute aqueous electrolytes with a high degree of accuracy at high temperatures and pressures. The results are complementary to our previously reported results measured with a static high-pressure cell, which was incapable of yielding reliable measurements at concentrations < 0.001 mol·kg-1 and densities < 0.4 g·cm-3. The new Λ0 values of all three hydroxides at densities (ρ) ≥ 0.5 g·cm-3 are in good agreement with those measured using the static cell. However, at densities below 0.5 g·cm-3 the new results are slightly higher and less scattered than the previous results at comparable conditions. On the other hand, the K A(m) values of all three hydroxides are in excellent agreement with the static cell results under analogous conditions.