304- Mr. Williams — Researches on Isomeric Alkaloids, [June ] 6, 



amylamine could scarcely be confounded with each other. On the other 

 hand, the two modifications of tartaric acid resemble each other so closely 

 in their chemical characters, that it is chiefly by the observation of 

 physical differences that they have been shown to be distinct. 



The most difficult cases to solve are where the substances to be studied 

 are so inert as to allow of few reactions by which they may be tested and 

 compared. Thus, up to the present time, no crucial test has been devised 

 by which the alcohol radicals can be distinguished from the isomeric hydro- 

 carbons of Boghead naphtha and American petroleum; and, indeed, a 

 change in opinion appears to be gaining ground, and the possibility of 

 their being identical seems again to be entertained by at least one chemist 

 who has carefully studied the subject*. 



Another and scarcely less difficult case presents itself where a substance 

 is supposed to be isomeric with another which at the time has no exist- 

 ence. Thus the constituent of oil of rue, long regarded as capric alde- 

 hyde, C^°H^°Ot, and which was subsequently shown to have the formula 

 Qii JJ22 -g jjy. some chemists §, who do not dispute the accuracy of the 

 latter formula, regarded as a ketone isomeric with the aldehyde of euodic 

 alcohol. But if the substance from rue oil be not the aldehyde, then the 

 real one is unknown, and consequently no means exist for a comparative 

 study. The question is, in this mstance, complicated by recent researches 

 indicating ketones to be the aldehydes of alcohols formed by the hydration 

 of olefiants |I . 



It is evident that the chances of isomeric bodies being formed in re- 

 actions, increase with the complexity of the type from which they are de- 

 rived ; or, in other words, the more replaceable hydrogen exists in the 

 type, the greater the chances of isomerism in the derivatives. The 

 ammonium and ammonia types always, therefore, present the greatest 

 number of instances of isomerism. 



In the course of the study of the organic bases produced by destructive 

 distillation, the author very carefully compared the reaction of alkaloids 

 from different sources, and he states that he was almost convinced of there 

 being a true chemical difference between the chinoline and leukoline series 

 before he succeeded in obtaining the decisive reaction resulting in the 

 formation of the blue iodides from the amyl compounds of chinoline and 

 lepidine. That observation led to the followdng comparative examination 

 of the pyridine series as obtained from cinchonine with the corresponding 

 series from Dippel's-oil and coal naphtha. 



In order to submit the alkaloids to a searching examination, it was 

 necessary that they should be in an equally high state of purity, and un- 

 dergo the same amount of fractionation. The methods of preparation and 



* Scliorlemmer, Chem. Soc. Journ., xvi. p. 428. 



t Gerhardt, Ann. de Chim. et de Phys. [3] xxiv. p. 103. 



% C. G. W. Phil. Trans. 1858, p. 199. § Hallwachs, Ann. Pharm. cxiii. p. 107. 



II Berthelot, Comptes Rendus, Ivii. 797, 63. 



