Phenidone

Phenidone (1-phenyl-3-pyrazolidone), the developing properties of which were discovered in the Ilford laboratories in 1940, possesses most of the photographic properties of metol together with some unique advantages. It shares with metol the property of activating hydroquinone so that a phenidone-hydroquinone (PQ) mixture forms a useful and very active developer. Used alone, phenidone gives high emulsion speed but low contrast, and has a tendency to fog. Mixed with hydroquinone, however, and with varying concentrations of alkali, phenidone produces a wide range of developers of differing types. The activation of hydroquinone requires a much lower concentration of phenidone than of metol. A detailed comparison of the relative merits of PQ and MQ developers is given later in this chapter.

More stable derivatives of phenidone have been proposed, especially for use in concentrated liquid developers. These include Phenidone Z (1-phenyl -4-methyl-3-pyrazolidone) and dimezone (1-phenyl -4,4-dimethyl-3-pyrazolidone).

Continue reading here: Restrainers antifoggants

Was this article helpful?