Voltammetry. Kolthoff became interested in voltammetry in 1933 when J. Heyrovsky, the inventor of polarography (voltammetry at the dropping mercury electrode) and future Nobel laureate, visited Minneapolis. Two of Kolthoff's top students, J. J. Lingane (Ph.D., 1938) and H. A. Laitinen (Ph.D., 1940) began working on voltammetry, Lingane on the fundamentals of the dropping mercury electrode, Laitinen on solid microelectrodes. In 1939 Kolthoff and Lingane published a 94-page paper in Chemical Reviews. This was followed in 1941 by an influential monograph with Lingane as coauthor, Polarography (Interscience, New York), expanded in 1952 into two volumes. Kolthoff with several of his students continued to study voltammetry, both in aqueous and nonaqueous solutions, into the 1960s.

Emulsion polymerization. In 1942 the Office of Rubber Reserve was set up to promote the production of synthetic rubber as a crucial part of the war effort. Kolthoff was one of several prominent professors, including physical chemist P. Debye, organic chemists M. Karasch and C. S. Marvel, and colloid chemists W. D. Harkins and J. W. McBain, invited to work with the major rubber companies. Kolthoff was asked to develop analytical methods so that the rates at which reactants were consumed could be determined. A key constituent turned out to be n-dodecyl mercaptan, referred to as "OEI," for "one essential ingredient."⁶ Kolthoff quickly developed an effective method for the determination of OEI based on amperometric titration at the rotated platinum microelectrode with silver nitrate. This method found worldwide use after the war, when it was published (1946). In typical fashion, immediately following this im-