Phenidone is an organic chemical compound whose primary use is as a photographic developer

Photographic developer

In the processing of photographic films, plates or papers, the photographic developer is a chemical that makes the latent image on the film or print visible. It does this by reducing the silver halides that have been exposed to light to elemental silver in the gelatine matrix...

. It has five to ten times the developing power as Metol

Metol

Metol is the chemical compound with the name monomethyl-p-aminophenol hemisulfate. It is a developing agent used in black & white photographic developers...

. It also has low toxicity and, unlike some other developers, does not cause dermatitis

Dermatitis

-Etymology:Dermatitis derives from Greek derma "skin" + -itis "inflammation" and genetic disorder.-Terminology:There are several different types of dermatitis. The different kinds usually have in common an allergic reaction to specific allergens. The term may describe eczema, which is also called...

upon skin contact.

Phenidone is Ilford's trademark for this material which was first prepared in 1890. It was not until 1940 that Dr. J. D. Kendall, in the laboratories of Ilford Limited, discovered the photographic reducing properties of this chemical.