Polarographic Behaviour of Some Sulphonic—aryl—hydrazono Dyes Pyrazolin-5-one Dyes

Abstract

Polarographic studies of some sulphonic aryl (or napthol ) hydrazono -I-phenyl -3-methyl -2-pyraz01in-5-one have been carried out in ethyl alcohol B. R. buffer solutions in the pH range 1.8 - 12.0. The nurrber of reduction waves was found to depend on the pH value of the solution and the structure of the dye stuff. All the conpounds gave a single, well defined irreversible wave between values 2.0-9.0. The E Of this wave is pH dependent but its i remains almst constant throughout the entire range. The E was shifted towards more negative potential showing that protonation preceeds reduction. The sulphonic group causes a shift of the wave and plateau suffers a minimum at value higher than 9.0. The reduction corresponds to consumption of four electrons leading to the amine stage. A general npchanism for the reduction process is suggested and discussed.