1985 年 105 巻 5 号 p. 481-490
Seventy seven crystalline organic drugs listed mainly in JPX were investigated by polarizing microscope by using the already reported improved immersion method. Thirty six drugs were classified as group A and 14 drugs as group B, from which two or one key refractive indices were measured, respectively. As for 26 drugs it was difficult to measure definite two refractive indices from their natural positions at the immersion method and they were classified as group C. However, two refractive indices were measured and described from their frequently observable positions. It was found that graphic representation of the correlation between refractive indices (n1, n2) and common logarithms of birefringence, log (n2-n1), was mostly convenient to use the results of polarizing microscopy for the purpose of analysis or identification of crystalline drugs not only in the cases of groups A and B, but also in the case of group C, sometimes by properly observing interference colors connected with birefringence.