Polarographic Determination of Small Amounts of Chromium in Calcium.

摘要

When a need arose for the determination of small amounts of chromium in calcium metal, a rapid, direct method involving no separations was naturally desired. Thus, two methods, colorimetric and polarographic, were suggested. Of the two, a polarographic method seemed the more promising. Demassieux and Heyrovsky (1), Spalenka (2), Prajzler (3), and Kolthoff and Lingane (4) have reported that chromium is reduced stepwise at the dropping mercury electrode giving two well-defined waves. The half-wave potentials are given as-0.88 volt and-l.53 volts vs. the saturated calomel electrode (S .C.E.) in 0.1 N potassium chloride (4). The first wave corresponds to the reduction of chromic ion to chromous ion, and the second to the reduction of chromous ion to the metal. With acid solutions of the chromic ion only the first wave is observable before the hydrogen wave.