Pararosaniline, Basic Red 9, or C.I. 42500 is an organic compound with the formula [(H2NC6H4)3C]Cl. It is a magenta solid with a variety of uses as a dye.[1] It is one of the four components of basic fuchsine. (The others are rosaniline, new fuchsine and magenta II.)[2] It is structurally related to other triarylmethane dyes called methyl violets including crystal violet, which feature methyl groups on nitrogen.
It is prepared by the condensation of aniline and para-aminobenzaldehyde. Alternatively, it arises from the oxidation of 4,4'-bis(aminophenyl)methane in the presence of aniline.
Pararosaniline is used as a colorimetric test for aldehydes, in the Schiff test. It is the only basic fuchsine component suitable for making the aldehyde-fuchsine stain for pancreatic islet beta cells.[4]
^Mowry, RW; Emmel, VM (1978). "Aldehyde fuchsin staining, direct or after oxidation: problems and remedies, with special reference to pancreatic B cells, pituitaries and elastic fibers". Stain Technology. 53 (3): 141–154. doi:10.3109/10520297809111457. PMID83035.
^GB 908634, "Pharmaceutical compositions containing pararosaniline or derivatives thereof", published 1962-10-24, assigned to Parke, Davis & Co.