It has been found I and confirmed 2 3 that the rate of anodlc oxadataon of zinc(0) from zinc amalgams as affected by the presence of cobalt(0), and it has been referred from the data that the reaction Β½Co 2 +Β½Zn 2 = CoZn occurs between dlatomic zinc and cobalt specaes This reference received some support from the report by Hovseplan and Shaln 2 that the currents obtained for the stripping of zinc from its amalgams in double-potential-step chronoamperometry were always smaller than they would have been ff they had been diffusioncontrolled. These authors conjectured that the differences reflected slow dlmerlzatlon of zinc m the amalgam phase.
Observations on the behavaors of mixed amalgams of copper and zinc 4 showed that the aggregation numbers of copper and zinc are equal m amalgams, so that if zinc is &atomic copper is also dxatomlc However, measurements of the potentials of copper amalgams in contact with solunons containing copper(II) showed that the half-reaction is Cu(II)+2e=Cu(Hg) rather than 2Cu(I1)+4e-Cua(Hg). We accordingly reanvestlgated the purported dlatomlc form of zinc(0) by double-potential-step chronoamperometry and by ~sop~estac measurements, with the results presented below.
DO UBLE-POTENTIAL-STE P CHRONOAMPEROMETRY
Double-potential-step chronoamperometrlc measurements were made with a dropping mercury electrode having a drop tame of 22 5 s in a solution contaming 0,01 M zmc(II), 0 1 M pyrldlne, 0.1 M pyrldmlum chloride, and 1 M sodmm perchlorate The potennal of the electrode was controlled with a Wenkmg potentlostat. The current was converted to a voltage by an operational amplifier connected as a current-to-voltage amplafler, and the tame dependence of this voltage was displayed on an oscilloscope and photographed