The redox potential as a critical factor in the hill reaction

Abstract The photochemical reduction of various quinones and dyes by water in the presence of chloroplasts was studied by measurement of the redox potential during illumination. Whether this Hill reaction will proceed to a measurable degree appears to be determined by the standard potential of the redox substance. With systems having a standard potential of about 40 millivolts Redox potentials in this paper are given with reference to the normal hydrogen electrode at pH = 6.5, and if possible at a temperature of 16° C. or lower, no reduction was observed.