- Phenidone (1-phenyl-3-pyrazolidinone) is an organic chemical compound whose primary use is as a photographic developer.
- It has five to ten times the developing power as Metol.
- Phenidone gives no fog with Low-Speed emulsion papers. However, with high speed emulsions it may produce fog.
- Phenidone is slightly soluble in cold water, but as the temperature of the solution increases Phenidone becomes more soluble, It is readily soluble in both acid and alkaline solutions.