Buffer Solutions of Potassium Dihydrogen Phosphate and Sodium Succinate at 25 °C

A buffer mixture consist in g of eq ua l molali t ies (m ) of potass ium dihydrogen phospha te and sodium succina te is proposed as a useful reference poin t in the study of acid-base equilibria, b ridging t he present gap be tween pH 5.5 a nd pH 6.8. The p(aH'YCI) at 25 °0 has been determined by elect.romo tive-fo rce measuremen ts for fi ve buffer solu tions in which m varied from 0.005 to 0.025. The conv()n t ional pall of each so lu t ion has been deri ved and found to be in good agn"ement wi th t hat calculated from existing data for the two eq uilibria concerned. Tho pall varies from 6.251 at m = 0.005 to 6.109 a t m = 0.025 . The buffer mixture has been used successfully for tho detcrmination of t he dissociat ion constan ts of 2-ni t ro-4-chlorophenol and 2,6-dichloroph enol.