Studies on the application of the quinhydrone electrode in formamide. IV. The ionization constants and related thermodynamic quantities of picric acid from E.M.F. measurements at different temperatures

Abstract

The e.m.f, of the cell                  Ag-AgCl/KCl(m₃), KPic(m₂), HPic(m₁), QH₂-Q|Au in formamide has been measured at 5° intervals over the temperature range 5-45°C. The pK_a value of picric acid ranges from 2.19 ± 0.12 at 5° to 1.16 ± 0.08 at 45°.