1. The infra-red absorption spectra between 1µ and 12µ of tropine, ecgonine, cocaine, tropacocaine, atropine, hyoscyamine, homatropine, noratropine, and scopolamine have been recorded and discussed. These substances may be readily differentiated by their sorption spectra.
2. Of the compounds examined, those containing the hydroxyl group are also readily identified by their absorption spectra.
3. The detection of the presence of the secondary amine group is very difficult, with the experimental method employed, when the hydroxyl group is also present.
4. No characteristic absorption of the tropan nucleus has been found.