The coloration of several nitrogen-containing compounds has been studied in connection with the aging of coal-derived liquid. It has been observed that the nitrogen-containing compounds having active N-H bonds are readily colored and the rate of coloration and reactivity toward 2, 2-diphenyl-1-picryl hydrazyl correlate well with each other. The irradiation of amines in methanol at visible light under air caused rapid coloration, but it was not observed in the absence of oxygen. Both peroxy and alkoxy radicals enhanced the coloration, but free radical scavengers were not effective in suppressing the coloration. The gel permeation chromatograms of the irradiated amines suggested the formation of high molecular weight compounds.
