Key refractive indices

Watanabe A, Yamaoka Y, Kuroda K. Study of crystalline drugs by means of polarizing microscope. III. Key refractive indices of some crystalline drugs and their measurement using an improved immersion method. Chem Pharm Bull 1980 28 372-378. 

In addition to morphological assessments of crystals, optical microscopy can be used to measure their refractive indices. To identify the crystal, it is not necessary to measure the principal refractive indices simply measuring two that are unique and reproducible is sufficient. These are termed the key refractive indices that, according to these researches, are all that are needed to identify any particular compound. 

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See also in sourсe #XX -- [ ]

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