The Exhaustion of Phenidone Developers by Aeration, and the Superadditivity of Phenidone with Hydroquinone Monosulphonate

Developer solutions containing Phenidone and hydroquinone, both carbonate and borate based, have been subjected to accelerated aeration. It has been established that although the Phenidone concentration in such solutions is usually low compared with that of the hydroquinone, its stabilization by the latter is such that the loss of Phenidone by oxidation is only slight even when the aeration is continued well beyond the point where the hydroquinone has been converted entirely to the sulphonate. The effect of EDTA on the course of such aerations has also been determined. The marked super-additivity of Phenidone with hydroquinone monosulphonate has been demonstrated experimentally, and the practical importance of this effect is discussed.