Abstract: In this paper, the ESR (electron spin resonance)spectra of brown and bituminous coal have been systematically studied by means of JES-FE1XG model ESR spectrometer.The brown and bituminous coals contain a large amount of stable free radicals. Due to strengthening of coalification, the peak width of bituminous coal is mo re narrow than that of brown coal. The efflorescence reaction results in obvious decrease of spin concentration, which will offer a quantitive standard for judging whether the coal was efflorescend. The reason may be that the structure of large molecule of coal is damaged by efflorescence reaction, resulting in the decrease of stability of π electron radicals.

Key words: Coal, Electron spin resonance spectrum, Free radical