The characterization of organic crystal products, based on internal structure using powder X-ray diffraction, was investigated with two substances. In the case of L-histidine alpha-ketoisocaproic acid complex ethanolate, the de-ethanolation rate increases when the crystal shows stronger intensities of (002) reflection. The difference of the intensities of the (002) reflection was found to be caused by the internal structure (i.e. degrees of crystallinity and preferred orientation). The layer structure of L-histidine alpha-ketoisocaproic acid complex ethanolate [1] could explain the crystal structure having the tendency to take a structure with preferred orientation. In the case of the alpha-form of L-aspartic acid, the degree of preferred orientation varies according to the crystallizing rates. Different crystal habits are noted among these samples. As a result of the simulation of a powder X-ray diffraction pattern from the crystal structure, the difference of the degree of preferred orientation is shown to reflect the global anisotropic displacement of molecules.
