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XIV. — On the Constitution and Properties of Picoline, a new Organic Base from 

 Coal-Tar. By Thojias Anderson, M.D. 



(Read, 20th April 1846.) 



The careful study of the products of destructive distillation has enriched 

 organic chemistry with an extensive series of results of unexpected interest and 

 importance. These results have affected, in no inconsiderable degree, the recent 

 progress of the science ; and their influence has been of a twofold character, both 

 general and particular, exerted in the former case in the development of some of 

 the more remarkable general doctrines of organic chemistry ; in the latter, in the 

 important light thrown by their investigation on the constitution of the substances 

 from which they are derived, and the facilities they have afforded of following out 

 connections, which the examination of the original substance either does not at 

 all present to our view, or, at least, indicates only in an imperfect or dubious 

 manner. Added to this, we have the remarkable fact of the appearance among 

 these products of substances in some cases identical with those occurring in 

 organised beings ; and in others, presenting analogies of the very closest charac- 

 ter with the actual products of vital affinity, which, taken together, afford abun- 

 dant reason for pursuing the investigation of substances which have already 

 afforded results of so remarkable a character. 



Setting aside altogether those substances, the occuirence of which is so fre- 

 quent, that they may be called the general products of destructive distillation, such 

 as carbonic acid, light carburetted hydrogen, olefiant gas, acetic acid, &c., it may 

 be laid down as a general rule, that each individual compound produced during 

 such a process, is formed by the destruction of a limited number of substances 

 only, which bear to each other, and to the product, a more or less intimate con- 

 nection in constitution or chemical relations. In those instances in which we 

 have been enabled to submit to destructive distillation substances of a definite and 

 simple constitution, in a state of chemical purity, and where an uniform tempera- 

 ture has been preserved, the results have been, for the most part, of an exceedingly 

 simple and intelligible character ; but in proportion as the atom becomes more 

 complex, so also do the products of its decomposition, and the explanation of the 

 results is found to be proportionately difficult and uncertain. These difficulties 

 and uncertainties are increased in a still higher degree, in the case of a substance 

 such as coal, where we have to deal not merely with one complex atom but with 

 a congeries of several such, and where the process is performed on the large scale, 

 and under a variety of perturbing influences. The distillation of coal is, in fact, 



VOL. XVI. PART II. 2 I 



