Phenidone—Part 1; The Mechanism of its Developing Action and its Super-additivity with Hydroquinone^*

* Read to the International Conference on the Science and Application of Pholography, organized by The Royal Photographic Society, London September 1953.

Abstract

A study has been made of the photographic behaviour of Phenidone and selected series of Phenidone-hydroquinone (PQ) developers, and their properties compared with those of analogous MQ developers. The results demonstrate the greater super-additivity of the PQ developing system, and have some bearing on current theories of development. Other experimental work on certain aspects of the chemistry of Phenidone shows that no sulphonation of the Phenidone takes place during development in the presence of sulphite. A mechanism for the PQ developing system is postulated which involves a coloured reversible mesomeric free-radical formed by the loss of an electron from the pyrazolidone ion.

Notes

* Read to the International Conference on the Science and Application of Pholography, organized by The Royal Photographic Society, London September 1953.