α-Phenylazo-β-naphthylamine was found to be a satisfactory reagent for the identification of aldehydes.This reagent does not react with acetone, acetophenone, cyclohexanone, and other ketones tested.Solid derivatives of twenty eight aldehydcs were prepared, the melting points ranging from 179 to 273°.The 1-anilino-2-alkyl-a-naphthoimidazoles react with hydrochloric acid to form salts, which in turn react with platinic chloride to form complex salts.With four exceptions all the 1-anilino-2-alkyl-a-naphthoimidazoles are fluorescent under ultra-violet light.