The standard analysis of coal by X ray diffraction (STAC-XRD), including evaluation of the number of aromatic layers in a stack (n), the average number of n (n (ave) ), the average distance between two aromatic layers (d002), and stacking index (SI), has been applied to several types of coals deashed and solvent-treated with hexane or methanol. Little influence of deashing was found on the distribution of n, as well as n (ave) , d002, and SI values. On the other hand, solvent treatment brought about almost the common changes for the coals employed, i.e., increase in n (ave) , and decrease in d002 and SI. These changes were explained owing to partial destruction of the loose stacking of the aliphatic layers attached to aromatic rings with the solvent treatment. The presence of the stacking of aliphatic carbons was suggested by taking into account a broad peak overlapped upon the 002 reflection peak due to aromatic carbons.
