SULFATE ELECTROSORPTION ON LIQUID GALLIUM FROM WATER

The electrosorption of sulphate ions on liquid gallium from aqueous so lutions of Na2SO4 + H2SO4 with concentrations ranging from 0.01 to 0.6 3 M was investigated on the basis of capacitive charge measurements ca rried out by a computerized chronocoulometric technique and of differe ntial capacity measurements. The unit slope of the Parsons-Zobel plot at zero charge and the concentration independence of the difference E - phi2 between the applied potential E and the Gouy-Chapman potential phi2 at the outer Helmholtz plane confirm the validity of the Gouy-Cha pman-Grahame theory. The potential of zero charge E(z) is independent of the electrolyte concentration and is equal to - 960 +/- 5 mV vs. a molar calomel electrode (MCE). A qualitative justification is provided for the difference between this E(z) value and the potential of zero charge, E(z) = - 920 +/- 5 mV/MCE, at the interface between liquid gal lium and aqueous solutions of the non-specifically adsorbed NaClO4 sal t.