pyr·rol, pyr·role n. Chem. A nitrogenous heterocyclic base found in coal tar, bone oil, and other distillates of organic substances, and also produced synthetically as a colorless liquid, C4H5N, having on odor like that of chloroform. It is the nucleus and origin of a large number of derivatives. So called because it colors a splinter of wood moistened with hydrochloric acid a deep red.
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