Polarographic studies of some sulphonic aryl (or napthol) hydrazono -1-phenyl-3-methyl-2-pyrazolin-5-one have been carried out in 10% ethyl alco­hol B.R. buffer solutions in the pH range 1.8 - 12.0. The number of reduction waves was found to depend on the pH value of the solution and the structure of the dye stuff. All the compounds gave a single, well defined irreversible wave between pH values 2.0-9.0. The E~ of this wave is pH dependent but itsremains almost constant throughout the entire pH 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 pH value higher than 9.0. The reduction corresponds to consumption of four electrons leading to the amine stage. A general mechanism for the reduction process is suggested and discussed.


F I ZIDAN ,B A EL SHETARY ,S L STEVAN ,M S A MOEZ ,