The paper describes a new phenomenon discovered in the electrolytic analog of a semiconductor
diode. As an example, the phenomenon is studied in the 0.1M KOH–0.1M HCl diode where
the
alkaline and the acidic reservoirs are connected by a hydrogel cylinder. First the
traditional, so-called positive salt effect is discussed. In that case some salt is
added to the alkaline reservoir of a reverse biased electrolyte diode and as a result,
close to a critical concentration of the added salt the electric current increases
sharply. The so-called negative salt effect appears as a suppression of the positive
one. It is shown by numerical simulations, by approximate analytical formulae, and
also by experiments that the high current caused by the salt contamination in the
alkaline reservoir can be mostly suppressed by relatively small salt concentrations
in the acidic reservoir. Thus a straightforward application of the negative salt effect
would be the sensitive detection of nonhydrogen cations in an acidic medium (eg.,
in ion chromatography)
