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X. — On the Oxidation Products of Picoline. By James Dewar, F.R.S.E., 

 Chemical Demonstrator in the University of Edinburgh, and Lecturer 

 on Chemistry at the Edinburgh Veterinary College. 



(Read 6th June 1870. ) 



The combined researches of Anderson and Williams on the basic compounds 

 contained in coal tar have led to the discovery of two well-defined series of 

 organic bases, called respectively the Pyridine and Chinoline series, the mem- 

 bers of both of which possess the properties of nitrile bases. The isomerism 

 between the pyridine and the aniline series of bases excited considerable 

 interest at the time of its discovery. The subsequent researches of Williams 

 on the products of the distillation of chinchonine led to the discovery of bases 

 having the same composition as the members of the pyridine and chinoline 

 series of coal tar. When first discovered they were supposed to be identical. 

 Since that time, however, a careful examination and comparison of the tar 

 series of bases with the chinchonine series has led Mr Williams to the interest- 

 ing discovery that the two lutidines, as also the two chinolines, are in reality 

 not identical, but isomeric. This introduces a greater complexity into the 

 study of the constitution of these compounds. 



I began this investigation in the summer of 1867 under the able direction 

 of Professor Aug. Kekul£, in the University of Ghent. At that time the 

 whole of the then known facts regarding the properties of these bases had been 

 accumulated by Anderson and Williams, and by Perkin, who had obtained 

 pyridine from a naphthaline derivative. Save by this latter method the only 

 process of preparation known was destructive distillation. All the attempts 

 that had been made to elucidate the internal constitution and relationship of 

 these bases had failed to yield positive results, their extreme stability in 

 presence of the most powerful reagents presenting a barrier to investigation. 

 In 1869 Professor Adolphe Baeyer made the brilliant syntheses of picoline 

 through the action of tri-brom-allyl and of acryl aldehyd, respectively, on 

 ammonia; and through the action of higher aldehyd homologues has shown the 

 reaction to be general. Thus, by the synthetical labours of Baeyer, we have 

 acquired for the first time a definite knowledge regarding the mode of forma- 

 tion and constitution of this class of organic compounds. 



Having formerly employed permanganate of potassium in the oxidation of 

 phenol (see Proc. Roy. Soc. Edin. Session 1866-67, p. 82), I naturally attempted 

 the oxidation of these bases by the same agent ; and I have since found that 

 vol. xxvi. part i. 3d 



