The heat of mixing a polar or nonpolar swelling solvent with coal was measured by flow microcalorimetry (FMC). Eight coals, having different oxygen contents, were used as the adsorbent, and methanol, THF, tetralin were used as the adsorbate. We examined a range of swelling solvent concentrations in n-hexane, 2-20 g/L, and found that there are large differences in the adsorption heats for the three solvents. Methanol adsorption heat reaches the maximum at low methanol concentrations and remains constant at higher concentrations, while heats for THF and tetralin adsorption increase with swelling solvent concentrations. The methanol adsorption heat maximum is about 2000 mJ/m(2), THF is 70 mJ/m(2), and tetralin is 40 mJ/m(2) over the concentration range 0-20 g/L. Uptake for swelling solvent was determined by comparing the concentration of swelling solvent in n-hexane before and after adsorption. Methanol uptake reaches about 80 mmol/g coal, while THF only reaches 0.3 mmol/g coal. Tetralin uptake is too small to be determined by such a technique. Similar to adsorption heat, methanol uptake reaches its maximum value at a lower concentration and then remains constant, and THF uptake increases with its concentration over the concentration range. We also investigated swelling of the eight coals in such swelling solvents and found that in contrast to methanol, THF has relatively low adsorption heats but large swelling ratios. This suggests that methanol likely interacts with specific sites on coal without disrupting coal-coal cross-links between macromolecular chains in coal, while THF may break such coal-coal cross-links. The low swelling ratios for tetralin suggest no disruption of coal-coal cross-links, although this solvent does interact with coal as seen from its moderate adsorption heat values. For coals swollen in a solvent, the heat for swelling Solvent adsorption on coal correlates strongly with coal swelling ratio in the solvent.