Electroanalytical study of the cobalt(II) pyridine—cobalt amalgam system, with application to stripping analysis

The electroreduction of cobalt (II) from solutions containing pyridine was investigated with stationary electrode polarography at a hanging mercury drop electrode using both single-scan and cyclic experiments. Scan rates ranged from 50 $\text{mV}\text{sec}$ to 110 $\text{V}\text{sec}$, and from the variation of the peak potential and the peak current function, i_p/V^v, (where i_p is the peak current, and v the rate of voltage scan) with scan rate, the reduction appeared to involve a reversible charge transfer followed by an extremely rapid chemical reaction in the amalgam to form a species not electroactive in the same potential range. This product appears to be a dimer or higher cobalt aggregate dissolved in the mercury. It is reoxidized at a potential about 1 V anodic of the reduction wave. This irreversible anodic wave was made the basis of a stripping analysis procedure for the determination of trace quantities of cobalt.