Reference value standards for pH measurements, and first ionization constants of o-phthalic acid, in ethanol/water solvent mixtures at temperatures from -5 to +40°C

Ref. value stds., pHRVS, for 0.05 mol/kg potassium hydrogen phthalate (KHPh) ref. buffer solns. in 10, 20, 40, and 70 wt% ethanol/water solvent mixts. from -5 to +40° were detd. from reversible emf. measurements. A large set of such emf. values (546 cells) was analyzed in terms of a multilinear regression method. Ancilliary values of the first ionization const. of o-phthalic acid (H2Ph; the parent acid to KHPh), required for the above calcns., were detd. also from reversible emf. measurements over the same range of solvent compns. and temps.