Physico-chemical studies on activity functions in some mixed solvents I Studies on lithium sodium and potassium hydroxide solutions in methanol water mixtures

ABSTRACT

The function of glass electrode, as a measure of acidity in terms of pH value, was studied for LiOH, NaOH and KOH solutions in methanol-water mixtures of different composition. The slopes of linear plots relating e.m.f. and pH values at different temperatures agreed well with those calculated theoritically. This indicated that the glass electrode behaved strictly as H2 electrode in all test solutions. The validity of Dole's theory of acid error delta E for the glass electrode indifferent alkali solutions was investigated. The number of water molecules associated with .the proton, in its migration from the solution into the glass surface, was determined and found to be unity. An attempt was also made to calculate the deviation delta of the pH-meter readings R[x] from the operational pH[j] values and the corresponding liquid junction potentials E[j] as well. delta and E[j] were found to be complex functions of alkali content, solvent composition and temperature probably due to changes in solvation and acidity coefficients of the ions in solution and also to the dielectric constant and basicity with additions of methanol to the purely aqueous solutions