Phenanthrene has been used to separate coals into four separate fractions. The exothermic reactions and swelling of 100 mg samples of these fractions and fractions plus coal were studied by means of a vacuum differential thermal analyzer.The thermograms show that swelling and exothermic reactions occur in only a cyclohexane soluble fraction. Only good coking coals produce such a fraction. This fraction is believed to contain the coking properties of coal. The swelling occurred at approximately 200 degrees C.Samples of the cyclohexane soluble fraction were added in amounts up to 20 percent by weight to both coking and non-coking coals. These additions do not appear to enhance the coking properties of such coals.