ISOMERIC CHANGE 621 



varying, indeed, in an arbitrary manner with the whim of each 

 individual writer — so that its true significance has been entirely 

 obscured. It is perhaps fortunate that the chaotic usage of the 

 word has, as a natural consequence, rendered it practically 

 obsolete at the present time, since it is likely that after a few 

 years the abuse of the word will so far have been forgotten 

 that it may once again become possible to use it in its original 

 sense. 



Reversal of Isomeric Change. — Only one further stage in the 

 history of isomeric change need be noticed at the present 

 moment. The distillation of cyanuric acid resulted in its 

 complete conversion into cyanic acid, which in its turn passed 

 over entirely into the porcelain-like cyamelide. So, too, when 

 ammonium cyanate was prepared by the action of ammonia on 

 the lead salt, the evaporation of the solution led to the appear- 

 ance of urea as the sole product of the action. For half a 

 century the impression prevailed that all isomeric changes must 

 be of this t}^pe, proceeding to completion in one direction or 

 the other according to the relative stability of the two com- 

 pounds. It is therefore impossible to speak too highly of the 

 investigations of Butlerow, which proved for the first time that 

 isomeric change might be reversible. Butlerow's observations 

 and the conclusions he drew from them provided a fitting 

 completion of the work begun by Wohler fifty years before, 

 and although the thirty years that have since elapsed have 

 provided innumerable examples in confirmation of his views, 

 they have, with one possible exception, added nothing to his 

 clear conceptions in reference to the phenomena of reversible 

 isomeric change. 



Butlerow's Work on Butylene and Bntylalcohol. — Butlerow's 

 discovery was made in the course of a series of experiments on 

 the conversion of the hydrocarbon butylene, C 4 H 8 , by the action 

 of sulphuric acid, on the one hand into butyl alcohols of the 

 formula C 4 H 10 O, and on the other hand into polymeric olefines 

 such as C 8 H 16 and C 12 H 24 . This investigation may be regarded 

 as an extension of the work of Faraday, to which reference has 

 already been made, on the relationship between ethylene C 2 H 4 

 and butylene C 4 H 8 , and formed part of a general study of the 

 polymerisation of the olefines and their interconversion with 

 the related alcohols. 



As early as 1873 Butlerow had noticed the presence of 



