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Anomalous x-ray diffraction and vibrational optical activity measurements are broadly used to determine absolute configurations of solid or liquid samples.

It may be said, however, that generally both the qualitative tests for, and the quantitative measurements of, the accelerating influence of enzymes depend upon the observation of some change in the physical properties of the substrate material, such as the optical activity, electrical conductivity, or viscosity, of its solution.

The glucosides, after extraction and purification by recrystallization, are generally colorless, crystalline solids, having a bitter taste and levorotatory optical activity.

Suffice it to mention that temperature plays an important part in the determination of the optical activity of certain essential oils, notably in the case of lemon and orange oils.

It must also be remembered that a cover glass, once compressed, may part with its acquired optical activity very slowly, and some time must be allowed to elapse before it is used again.