Phenidone (1-phenyl-3-pyrazolidinone) is an organic compound that is primarily used as a photographic developer. It has five to ten times the developing power as Metol, capable of achieving the same level of development in both less time and at a lower concentration.[1] It also has low toxicity and unlike some other developers, does not cause dermatitis upon skin contact.[2] As a developer, Phenidone is typically used in conjunction with hydroquinone for black and white photography and performs better at lower pH levels.[3]
Phenidone is Ilford's trademark for this material, which was first filed on Feb. 24, 1953, but has since expired.[4] Although the compound was first prepared in 1890; it was not until 1940 that J. D. Kendall, in the laboratories of Ilford Limited, discovered the reducing properties of this compound. Large scale production did not become feasible until 1951.[5]
Phenidone functions as a reducing agent. It converts to the N-phenyl-hydroxypyrazole. It is oxidized in acidic conditions, contributing the electrons it loses to reduce silver halides such as those found in film:[6]
Reaction of phenidone with silver bromide, as occurs in photographic development
Phenidone is also a dual cyclooxygenase/lipoxygenase inhibitor, capable of blocking the synthesis of arachidonic acid, which plays a role in causing inflammation in systemic inflammatory response syndrome[7] and neuronal damage in kainic acid-induced seizures.[8]
