Abstract: PABA exhibites a well defined single peak in Osteryoung (modern) square wave polarogram in a supporting electrolyte, solution of 0,5M(C₂H₅)₄NBr, The peak potential is -1.529±0.006V(Ag/AgCl) at 18℃, The results proved that the polarographic peak is a hydrogen catalytic wave, There is a lineare relation between catalytic current and PABA concentration from 2.9×10^-5 to 1.2×10^-3M, The rate constant of electrode reaction is 9.7×10^-4cm/s and the. transfer coefficient is 0.56. A mechanism involving radical formation and proton discharge at a hanging mercury drop electrode has been proposed.

Key words: Polarographic catalytic wave, p-Aminotenzoic acid, Osteryoung square wave