Dr. E. J. Mills on Isomerism. 9 



many instances. Thus, for example, one-sixth of the hydrogen 

 in hydric lactate is easily replaced by positive, and another sixth 

 by negative radicals. If, by an artifice, replacing radicals of an 

 opposite sign are introduced*, an isomeric series of compounds 

 is originated. The same is true of hydric glycollate. Again, 

 the nitryl in a-nitraniline differs from that in /3-nitraniline; and 

 dinitromethylenic chloride contains at once nitryle in two con- 

 ditionsf. Toluol, when acted on by chlorine in the cold, pro- 

 duces chlorotoluol X ; but when chlorine is passed through boil- 

 ing toluol, benzylic chloride is the result §, It can scarcely be 

 doubted that the function of chlorine is different in these two 

 compounds. In addition to the difference indicated by the 

 names just assigned to them, they yield opposite products on 

 oxidation, — chlorotoluol furnishing hydric chlorodracylate, while 

 benzylic chloride gives hydric benzoate and hydric chloride J. The 

 chlorine in both bodies is combined with the same quantities of 

 carbon and hydrogen ; and though these latter elements doubt- 

 less have an influence on the behaviour of the chlorine, there 

 seems to be no escape from the conclusion that the different 

 relations which it exhibits in the two cases constitute a separate 

 and distinguishable phenomenon. If it be alleged that this 

 oppositeness is not due to the chlorine, but solely to the radicals 

 with which it is respectively combined, then it follows that these 

 radicals are themselves endowed with permanently opposite 

 functions, thus equally establishing the doctrine of fixed induc- 

 tive effect for which I contend. Similar instances to those 

 already cited will readily present themselves to the mind of every 

 chemist. 



It will be easily perceived that the possibility of inducing a 

 permanent difference in radicals affords us a means of account- 

 ing for all the isomers at present existing, and of foreseeing the 

 formation of many more. The explanation applies obviously to 

 metamers ; for in them different quantities of a given element 

 or elements are counted under opposite functions. It is appli- 

 cable also to polymers ; for they are only particular cases of che- 

 mical combination ||, and therefore also liable, to the manifesta- 

 tion of permanent induced difference. And so far as the various 

 allotropic forms of the elements shall prove analogous to ordi- 

 nary isomers and polymers, so far, it may be presumed, the 

 same explanation will apply to them. Physical isomerism ought 

 not to be placed apart from chemical isomerism. Differences of 

 solubility, fusion-point, action on polarized lights &c. are phases 



* Compare Watts's ' Dictionary of Chemistry/ vol. iii- p. 463. 



t Chem. Soc. Journ. [2] vol. ii. p. 156. 



X Ann. der Chem. und Pharm. vol. cxxxix.p. 338. 



§ Ibid. vol. xcvi. p. 246. || Legons sur I'Isomerie, p. 19. 



