pH Standardization of 0.05 mol·kg-1 Tetraoxalate Buffer at Temperatures from (5 to 45) °C with Added KCl Molality up to 1.0 mol·kg-1

The standard pH of 0.05 mol·kg-1 potassium tetraoxalate was determined using the calculation method recommended by IUPAC (Pure Appl. Chem. 2002, 74, 2169−2200) at various temperatures from new Harned cell data and literature data. New data were obtained for 0.05 mol·kg-1 potassium tetraoxalate solution containing up to 1 mol·kg-1 KCl at temperatures of (5, 15, 25, 35, and 45) °C. One step in the calculation method of IUPAC is a linear extrapolation of the experimental quantity p[a(H+)γ(Cl-)], where a refers to the activity and γ refers to the activity coefficient, to zero molality of KCl. The possibilities of using more concentrated KCl solutions in this determination with nonlinear extrapolations were also investigated.