Conductance of the hydroxide ion intert-butyl alcohol-water and 1,4-dioxane-water mixtures

Abstract

Limiting molar conductances λo of potassium hydroxide in 2 to 25 mol%tert-butyl alcohol (TBA)-water mixtures were determined at 25°C as a function of pressure up to 196 MPa. λo’s of KOH in (2.5 to 15 mol%) 1,4-dioxane-water mixtures at 25°C and 1 atm were also determined. The excess conductance λoe of the OH- ion estimated as [λoe(OH-) = λo(KOH) - λo(KCl)] decreased with an increase in the TBA or dioxane content, as did the excess proton conductance λoe(H+) [λoe(H+) = λO(HC1) - λo(KCl)]. Although λoe(OH-) is smaller than λoe(H+) at all solvent compositions studied, the rate of decrease in λoe with organic content is larger for the OH- ion than for the H3O+ ion in both solvent mixtures except in the water-rich region of TBA-water mixtures. λoe(OH-) increases with pressure more strongly in TBA-water mixtures than in pure water, and the rate of increase in λoe (OH-) with pressure has a maximum at 5 mol% of TBA. These results are discussed in terms of the difference in stability of hydrogen bonds between the OH- or the H3O+ ion and water molecules and the increase in repulsive forces due to the orientation [H-O O-H] of water molecules in the mixtures.