Second dissociation constant of oxalic acid from 0 to 50 C, and the pH of certain oxalate buffer solutions

Abstract

The second di ssociation constant of oxali c acid was determined at interval s of 5 d egrees from 0° to 50° C by measurement of the electromotive force of cells without liquid junction. Hydrogen a nd sil ver-sil ver-ch lorid e electrodes were employed. The so l u tions were composed of potassium binoxalate, sod ium oxalate, and sod ium ch loride. The valu e of the second dis-soc iation con tant, 1(2, in t he tempe ratu re range st udi ed is given by the equation 1423.8-log K 2=-T-6.5007 + 0.020095T, wh e re T is the abso lu te temperature. Th e thermodynamic quanti ties associated ,yilh the second di ssociation step were calculated. The paH values of 8 soLu t ions of potassium binoxa-late and sodium oxalate in the ratio 1:5 were determined at 11 temperatures.