THE 

 LONDON, EDINBURGH, and DUBLIN 



PHILOSOPHICAL MAGAZINE 



AND 



JOURNAL OF SCIENCE. 



^ 



[FIFTH SERIES.] 



SEPTEMBER. 



XXII. On Isomerism. By M. M. Patttson Muir, F.R.S.E., 

 Assistant-Lecture?^ on Chemistry, the Owens College, Man- 

 chester *. 



1. ~|~N a paper published in this Magazine ([V.] vol. ii. 

 i- p. 1) I upheld the proposition that our ordinary 

 chemical notation indirectly expresses changes in the form of 

 the energy of a system of bodies reacting chemically upon one 

 another. Among the phenomena which are undoubtedly con- 

 nected with such changes of energy isomerism holds an im- 

 portant position. I endeavoured to show that the facts of 

 isomerism, while pointing to differences in the energies of 

 the isomeric bodies, were not inconsistent with the generally 

 accepted theory, according to which isomeric molecules are 

 possessed of different atomic structures. 



I shall now endeavour to supplement the remarks made in 

 the paper referred to by others having a similar hearing. 



2. The " position theory" of isomerism would seem to ac- 

 count for the phenomena by assigning to the atoms which form 

 two isomeric molecules different positions in the two molecules ; 

 the " energy theory " of isomerism would trace the cause of 

 the phenomena to those " conditions of action under which 

 forces effect a fixed alteration in one or more functions of 

 radicles." 



But these theories are not, it seems to me, incompatible. 

 Changes of function are associated with changes of energy, 

 and these again with changes in the " configuration of a 

 material system." 



* Communicated by the Author. 



Phil. Man. S. 5. Vol. 2. No. 10. Sept. 1876. M 



