Abstract
It was clarified in previous report that the predominant faces of crystal habits mainly coincide with the morphologic crystal face at (001), (010), or (100), and therefore the two measurable key refractive indices are closely related to the principal sections of the two axial wave surfaces and coincide with the one or two of the three principal refractive indices. The three principal refractive indices of biaxial crystalline drugs were measured and tabulated in the “General Information” section of the National Formulary compiled by the American Pharmaceutical Association. A series of studies was conducted to measure the key refractive indices of the crystalline drugs listed in the Japanese Pharmacopoeia X or XI so that the data could be used to improve the quantitative analysis of their crystal habits. The purpose of the present study was to examine data on both the key and principal refractive indices and attempt to produce a general authorized table of optic crystallographic characteristics, including crystal habits, for simpler and more reliable polarizing microscopy studies.
