Electrode Potentials of Hermidin, the Chromogen of Mercurialis perennis.

HAAS and HILL [1925, 1] have recently directed attention to a chromogen of considerable interest which escapes from the plasmolysed cells of Mercurialis perennis. If the coarsely divided tissue be steeped, anaerobically, in chloroform water for a short time, there results an extract which, on exposure to oxygen, assumes first a rich blue and then a yellow-brown colour. These investigators [1925, 2] have further shown that, within the experimental limits imposed by the difficulty of arresting the oxidation exactly at the stage of maximum intensity of blue colour, the two successive reactions are attended by an equal absorption of oxygen. The oxidation to the blue substance (cyanohermidin) was demonstrated to be readily reversible and Haas and Hill [1926] were further persuaded that the second stage of oxidation is also, at least partially, reversible, although they were unable quantitatively or consistently to effect the reduction of the yellow compound (chrysohermidin) through the blue to the chromogen. The data presented in the papers cited suggested that the systems involved might be amenable to electrometric study and the present paper reports the measure of success attained. The application of electrometric methods to organic systems has been extensively discussed in its theoretical aspects by Clark and Cohen [1923, 1]. The general relations may be summarised in a form of the Nernst electrode equation E =E'o RT log[St]