Mr. M. M. P. Muir on Isomerism. 165 



N Ti b r yli !} cH '- cH ^- cH ^- cH - oH2B - p=ii6 °- c - 



Isobutylic alcohol CH 3 — CH— CH 2 —OH „ 109°,, 



CH 3 

 S Tci7 bUtyli ° } CH 3 -CH 2 -CH-CH 3 „ 97° „ 



OH 

 CH 3 



OH 



So, again, we learn from experiment that a substance whose 

 reactions are best expressed by writing its formula as contain- 

 ing the group OH, is generally possessed of a higher boiling- 

 point than another isomeric substance which does not appear 

 to contain this group ; hence from a consideration of the 

 boiling-points of ethyiic alcohol, and of methylic ether respec- 

 tively (78° and — 21° C), and from a knowledge of the two 

 possible modifications of the empirical formula (C 2 H 6 0), 

 which is common to each, we should expect, without a pre- 

 vious study of the reactions of these bodies, that the structural 

 formula of the alcohol would be CH 3 — CH 2 — OH, and of the 

 ether CH 3 — 0-CH 3 . 



More careful and extended observations of the boiling-points 

 of isomeric compounds will doubtless throw considerable light 

 on their molecular structure. The specific volumes of isomeric 

 bodies are also, it would appear, connected with their mole- 

 cular structure. Thus according to Kopp the specific volumes 

 of acetic acid and methylic formate are almost identical ; their 

 structural formulae are likewise analogous, viz. CH 3 — CO — OH 

 and H-CO-0-CH 3 respectively. 



The researches of Thorpe, part of which have been already 

 published, will probably help to elucidate the connexion which 

 exists between specific volume and isomerism. 



From a study of the heat of combustion and of formation of 

 isomeric substances, we may also hope for knowledge concern- 

 ing the second part of the general problem of isomerism. 

 May we not suppose that in certain isomers the energy exists 

 in a more available form than it does in others, perhaps even 

 in other members of the same group ? We know that under 

 certain conditions energy may be in a more available form 

 than under other conditions ; is there such a difference in the 

 energy of isomers ? Supposing that this is the case, availability 



