The Identification of Aromatic Polycyclic

In previously reported experiments, the car cinogenic potency for mice of extracts of processed rubber was traced to the presence of 3,4-benz pyrene and related compounds (13). A search for the origin of these hydrocarbons was next under taken. Samples of crude rubber, both natural and synthetic, did not contain any of these hydrocar bons when they were sought by extraction, chro matography, and ultraviolet spectrophotometry.' A study of a typical formula for the processing of rubber suggested carbon black as the most likely source of the hydrocarbons. Samples of 24 carbon blacks were then examined by methods similar to those mentioned above. The absorption spectra of 3,4-benzpyrene and six related aromatic hydro carbons were detected in a great number of the carbon blacks. The aromatic hydrocarbons found in carbon blacks were the same as those identified in processed rubber except that (a) coronene was found in carbon blacks but not in rubber and (b)