DETERMINATION OF BISMUTH AND LEAD BY CONTROLLED-POTENTIAL COULOMETRIC OXIDATION

A method has been developed for the determination of lead and bismuth by controlled-potential coulometric oxidation. After simultaneous reduction of both metals into a mercury pool, lead and bismuth are determined by stepwise anodic stripping at -0.16 and +0.20 V vs. Ag/AgCl/sat. KC1 electrode, respectively, in a supporting electrolyte of 0.4 M tartaric acid and 0.30-0.72 M perchloric acid. The reduction of lead and bismuth is carried out at -0.50 V or more negative potential. Bismuth alone can be reduced at -0.25 V. Polarography with a dropping amalgam electrode was advantageously applied to establish optimum conditions for coulometric oxidation of these metals. Solutions containing 0.02-0.2 meq of lead and/or bismuth were analyzed with an accuracy and precision of ±0.2% or better for lead and ±0.3% for bismuth. The method was applied to the analysis of glasses and thin films. © 1969.