The infrared absorption spectra of sulphonamides, when compared with the spectra of Authentic Specimens, provide a simple and complete means of identification, provided the effects of polymorphism are excluded. Of 18 substances examined, twelve showed evidence of polymorphism. Limited solubility prevents the use of solution spectra, and specified solvent treatments, details of which are given, may therefore be necessary with these substances to ensure reproducible spectra.
The polymorphism of phenobarbitone has been investigated using infrared spectroscopy, X-ray diffraction and differential scanning calorimetry. Eight crystalline modifications have been isolated and shown to have distinguishable infrared absorption spectra and X-ray powder diffraction patterns. Other forms were found to be present in mixed crystals and molecular compounds obtained from mixtures of phenobarbitone with other barbiturates. Differential thermograms of three forms of thialbarbitone are also given.
The infrared absorption spectra of steroids, when compared with the spectra of Authentic Specimens, provide a simple and complete means of identification, provided that the effects of polymorphism are precluded. Of 35 substances examined, 16 showed no evidence .of polymorphism and a further twelve were sufficiently soluble to be examrned In solution. Specific solvent treatments, details of which are given, may be necessary with the remaining seven substances if the spectra of the sample and of the Authentic Specimen are not identical when first examined.
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