THE 

 LONDON, EDINBURGH, and DUBLIN 



PHILOSOPHICAL MAGAZINE 



AND 



JOURNAL OF SCIENCE. 



[FOURTH SERIES.] 



JANUARY 1867. 



I. On Isomerism. By Edmund J. Mills, D.Sc, F.C.S.* 



THE object of the following paper is, in the first place, to 

 give a brief historical summary of the leading opinions 

 relating to isomerism ; and secondly, to advance a general 

 theory respecting it. 



I. 

 According to Berzeliusf, the first definite opinion on the sub- 

 ject of isomerism was that of Stromeyer, who expressed it in 

 these terms : — " The difference between ignited phosphoric acid 

 and that which has been long in solution does not consist m a 

 quantitative difference of composition ; it can only be explained 

 by the dissimilar manner in which the elements are united with 

 each other, and the unequal degree of condensation they thereby 

 undergo." Before the enunciation of this view (which it will be 

 perceived is essentially mechanical) Berzelius himself had made 

 known the existence of two stannic oxides ; and having now com- 

 pleted a comparative study of racemic and tartaric acid, he annexed 

 to an account J of these substances the first outlines of a special 

 nomenclature. Isomeric bodies are " those which, with the same 

 chemical composition and atomic weight, have different proper- 

 ties." When there are only two isomers in a group, irapa (as 

 used in irapdho^ov) is to be prefixed to the name of the one more 

 lately discovered. The adjective metamorphic may, however, be 

 used instead of the prefix. The dimorphism of different salts does 

 not affect their isomerism, the former being merely a mechanical 

 effect. The different states assumed by carbon are mentioned, 



* Communicated by the Author, 

 t Jakresbericht, 1832, p. 45. 



t Ann. der Phys. [3] vol. xix. p. 305 (1830) ; Ann. de Chim. et de Phys. 

 vol. xlvi. p. 136. 



Phil. Mag. S. 4. Vol. 33. No. 220. Jan. 1887. B 



