Paraphenylenediamine

Paraphenylenediamine - reducing agent used in some fine grain and color developers.
Paraphotography - general term for non-silver-halide image forming processes.
Paraxial - rays nearest the optical axis of a lens.

Hydroquinone, Metol, paraphenylenediamine, and phenidone are some of the more commonly used developing agents. PRESERVATIVE All developing agents in an alkaline state are affected by oxygen.

See also: Development, Element, Bromide, Carbonate, Gelatin