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Notes 6329 described above. Elution of the exposed areas of these chromatograms and rechromatography in ligroin-propylene glycol and exposure of the strip to the Zimmermann reagent revealed the presence of additional steroid presumed areas, apart from those of the unchanged steroids. Several such chromatograms are illustrated in Fig. 3. DiscussionThe so-called "decomposition" of steroids when exposed to oxygen (or air) and to various forms of radiant energy (ultraviolet light, X-rays) has been recognized for some time. That these effects on the stability of steroids occur during paper chromatography is not unexpected since the steroid is usually spread over a considerably large area which affords maximal conditions of exposure to light and to air. The observations reported here indicate that ultraviolet light (present in artificial light and sunlight) can effect chemical changes in steroid samples during the drying of a paper chromatogram.Other occasions of likely exposure of a steroid preparation to light and to air can and do occur in the course of the various manipulations inherent in the paper chromatographic technique (application of sample to the starting line, development of the chromatogram).• It has been noted that ,ß-(6) D. H. Peterson, private communication.(7) W.

The second dissociation constants representing the transition from monocation to dication for all of the isomeric aminoquinolines have been determined as pKa' values. The analogous values for 2‐ and 4‐aminopyridine have been recalculated using a revised HO scale. The accurate determination of the second pKa values follows from measurement, for the first time, of the ultraviolet spectra of all the mono‐ and dications of the aminoquinolines.

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