the trademark for l-phenyl-3-pyrazolidone, a compound occurring as white, yellowish, or grayish acicular crystals. The structural formula is
Phenidone has a melting point of 121°C (according to other data, 118°–122°C); 1 g of the compound dissolves in 10 cm3 of either boiling water or hot alcohol. Phenidone is soluble in dilute acids and dilute solutions of alkalies, but it is insoluble in benzene. The compound is a strong reducing agent.
Phenidone is obtained through the condensation of phenylhydrazine with β-halopropionic acid. It is used in photography as a developing agent, usually in a mixture with developers.