抄録
We have succeeded to estimate h_f of coal from the number and the energy of bonds among C, H, and O atoms in coal molecule. It made possible to discuss the chemical structure of coal based on the number of aromatic carbon bonds and that of aliphatic one or C_l-C_l. The number of C_l-C_l bond in coal is evaluated in the range of about 2 to 3 for lignite, 2 to 8 for sub-bituminous coal, 2 to 6 for bituminous coal, 2 to 4 for high rank bituminous coal and 0.3 to 2 for anthracite.