Tensammetry: A Method of Investigating Surface Phenomena by A.C. Current Measurements

A new type of investigation into surface phenomena, "tensammetry", has been developed by superimposing a small sinusoidal A.C. voltage upon the direct potential applied to a dropping mercury electrode in the presence of surface active substances and measuring the resultant A.C. currents. Wave shaped current-voltage curves are thus obtained which have their origin in adsorption processes occurring at the electrode. These waves are attributed to the movement of surface active molecules in the region of "active space" near the electrode without actual electron transfer across the electrode boundary; that is, the electrode remains polarized with respect to U.C., but is depolarized with respect to A.C. The general properties of tensammetric waves of a number of organic compounds together with their effects on one another and on D.C. and A.C. polarographic waves have been investigated. The theoretical basis and the fundamental equations governing the tensammetric, process are derived and discussed.