9-Phenylacridine is the parent base of chrysaniline or 3,6-diamino-9-phenylacridine, which is the chief constituent of the dyestuff phosphine (not to be confused with phosphine gas), a by-product in the manufacture of rosaniline. Chrysaniline forms red-coloured salts, which dye silk and wool in a fine yellow; and the solutions of the salts are characterized by their fine yellowish-green fluorescence. Chrysaniline was synthesized by O. Fischer and G. Koerner by condensing ortho-nitrobenzaldehyde with aniline, the resulting ortho-nitro-para-diamino-triphenylmethane being reduced to the corresponding orthoamino compound, which on oxidation yields chrysaniline.