Standards for pH measurements and first ionization constants of o-phthalic acid. Methylcellosolve-water solvent mixtures from -10 to 45°C

From reversible emf. measurements of the cell Pt|H2|KHPh + KCl|AgCl|Ag|Pt, ref. value pH-metric stds., pHRVS, for 0.05 mol-kg-1 potassium hydrogenphthalate (KHPh) ref. buffer solns. in 20, 50, and 80 wt % methylcellosolve (2-methoxyethanol, CH3O-CH2CH2OH)-water solvent mixts. from -10 to +45°, have been detd. in compliance with the criteria endorsed by IUPAC. The corresponding values of the first ionization const. of o-phthalic acid (H2Ph, benzene-1,2-dicarboxylic acid), which is a key quantity for the acquisition of pHRVS stds., have been detd. from emf. measurements of the reversible cell Pt|H2|H2Ph + KHPh + KCl|AgCl|Ag|Pt.