“…Sir: Many modifications of Heyrovsky's polarograph and numerous methods of polarographic analysis have appeared in the literature (1, 2, 5, 9). The development of commercially available polarographs and current methods of polarographic (3,4) and amperometric (6,7) analyses are reviewed periodically. The application of polarographic and amperometric methods to trace analyses has created a need for polarographs capable of measuring very small currents.…”