Equilibrium Composition of 1-Butanol–Water–Alkali Hydroxide System and Distribution of the Base

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Equilibrium compositions of 1-butanol–water–MOH systems were studied at 25 °C, where MOH represents LiOH, NaOH, and KOH. Water and 1-butanol were determined by means of gas chromatography and the bases by titration. Apparent distribution ratio Kobs (molality of MOH in the aqueous phase/molality of MOH in the 1-butanol phase) was dependent on the concentration of base. A considerable amount of water was transferred from 1-butanol to the aqueous phase giving rise to an increase of base concentration. This suggests that the variation of Kobs depends principally on the variation of solvent composition. Kobs was expressed semi-empirically, considering the activity coefficients calculated by Miller's equation and also the change in the standard free energy resulting from the variation in solvent composition. Decrease of 1-butanol in the aqueous phase with the base concentration obeyed the salting-out equation. The calculated salting-out coefficients were: LiOH 0.176, NaOH 0.192, and KOH 0.184. These values are correlated to Gurney's unitary entropy. The results were compared with those previously obtained for alkali halides.
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