Abstract
To obtain necessary characterizations of crystals, such as an extinction angle, an elongation, refractive indices and a birefringence, several polarizing photomicrographs taken under definite conditions by the immersion method using a kit of immersion oils prepared at intervals of 0.005 between nD 1.470-1.730 were found to be useful enough. A standard procedure to take the least sheets of necessary photomicrographs using the known key refractive indices was proposed, and 8 kinds of crystalline drugs of which key refractive indices had been measured definitely (group A) except the last one showing only one key refractive index (group B) were tested together. It was also found that habit parameters as well as habit coefficients useful to obtain a particle size distribution were easily measured from orthographic projections produced from colored photomicrographs and the above obtained birefringences.
