Studies on the application of the quinhydrone electrode in formamide. VII. The ionization constants and related thermodynamic quantities of (E)-cinnamic acid from E.M F. measurements at different temperatures

Abstract

The e.m.f. of the cell Ag-AgCl/NaCl(m3), NaA(m2), HA(m1) QH2-Q/Pt (where HA is cinnamic acid) in formamide has been measured at 5� intervals over the temperature range 5-45�C. The pKa value of (E)-cinnamic acid ranges from 7.02 � 0.03 at 5� to 6.78 � 0.05 at 45�.