Dr Anderson on the Properties of Picoline. 297 



determination of their atomic weights, without which tlie 

 isomerism cannot be admitted as proved. The other in- 

 stance is that of bebeerine, which, according to the analyses 

 of Dr D. Maclagan,* is isomeric with morphia, both being 

 represented by the formula C35 H^o N Og ; and as this result 

 is supported by the analysis of the platinum compound, the 

 probability of their isomerism is much higher than in the for- 

 mer case. Unfortunately, however, another source of fallacy 

 enters into the question in the amorphous condition of be- 

 beerine, which renders it impossible to determine with cer- 

 tainty its freedom from impurity ; even the constitution of 

 morphia, by far the most definite of the two substances, can 

 scarcely be considered as fixed, Gerhardt, for instance, re- 

 presenting it by the formula C^ H19 N Og, and not by that 

 formerly given. 



With aniline and picoline, however, these uncertainties 

 disappear. Both substances are possessed of definite boiling 

 points widely different from one another, and of all the other 

 physical characters of pure substances. The lowness of their 

 atomic weight also precludes any possibility of doubt regard- 

 ing the true formula, and enables us to speak with certainty 

 as to the identity of their constitution. The isomerism of 

 these substances is, moreover, of much higher interest in a 

 theoretical point of view. Menispermin and morphia are 

 isolated substances, entirely unconnected, in constitution or 

 general relations, with any other substance. Aniline, on the 

 other hand, is a member of one of the most extensive, widely 

 distributed, and interesting groups of substances, with which 

 the recent discoveries of organic chemistry have made us 

 acquainted, the Indigo Salicyl and Benzoil series. The 

 members of this large group already present a variety of 

 instances both of isomeric and polymeric compounds, a few 

 of which I have here brought together in the form of a table, 

 which does not pretend to any scientific arrangement, its sole 

 object being to point out the remarkable relations of aniline 

 and picoline to the group. 



* Pi-oceedings of the Royal Society of Edinburgh, No. 26. 



