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

Abstract

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.

Catalytic and Kinetic Waves in Polarography

“…Thus, using Breyer's method (applying at the electrode, together with a dc potential, a superimposed small sinusoidal potential, and making the ac component independent of the linearly increasing dc electrode potential [250][251][252]) the electrode process of U (VI) reduction to U (V) was investigated, with disproportionation of U(V) to U(VI) and U(IV) [253]. The current measured by Breyer's method seems to be the sum of the active and capacitance component and therefore cannot be quantitatively evaluated; the results obtained by this method are only qualitative.…”

“…Qualitative data on the adsorption of compounds and also on the potentials of desorption can be determined as was mentioned in the previous section on the so-called Breyer polarograms [252]. These curves gi ve the dependence of the variable component of the current on the potential of the dropping electrode if a smaller sinusoidal voltage is applied at the electrode simultaneously with the constant voltage.…”

Comparative study of the effect of some macro-molecules and some simple molecules on dropping mercury electrode capacity

“…These features were confirmed by the more precise measuremerits of Grahame (6). The pulsating field technique (5) was shown in this laboratory to be very convenient for the investigation of these phenomena (7) and later but independently by Breyer and ttaeobian (8). Interesting results have been obtained with regard to the behavionr of bromocresolpurple at the mercury aqueous interfaces (9,10).…”

A.C. Polarographic-Tensammetric Transition waves

“…(ii) The base current on the positive side of the summit potential was considerably depressed, indicating the presence of a surface active substance at the electrode (cf. Breyer and Hacobian 1952). The fact that the base current is decreased on the positive side of the summit potential and towards the lower part of the D.C. polarographic step, shows that the surface active substance is mercurous halide, formed at the electrode boundary by the halogen ion discharge.…”

“…Breyer, Gutmann, and Hacobian 1950a, 1950b, 1951Hacobian 1951a, 1951b) or of surface active substances (Tensammetry ; Breyer and Hacobian 1952). In the case of A.C. polarography, the waves have their origin in electron transfer across the electrode boundary, whereas tensammetric waves are due to adsorption-desorption equilibria at the electrode-solution interface, without electron transfer.…”