98 J. Thomsen’s Thermochemical Investigation, ete. 
& 2 
Cc C 
ere ae Sets 
c Cc c—|—ec 
| oe | I 
a Cc c—/|—c 
Sqr Sage” 
In the first scheme there are three single and three double 
bonds; in the second scheme nine single bonds. Making now 
the obvious substitutions in equation (18), we obtain for the 
heat of formation under constant volumes either 
—60,360° or —16,650°, 
and for the heat of formation under constant pressure 
—59,200° or —15,490°, 
We can now easily calculate, by the method already described, 
the heat of combustion of benzol vapor and we shall obtain 
846,040° or 802,330°. 
Finally, Thomsen has re-determined with great care the same 
value and finds as the mean of five experiments that the heat 
of combustion of the molecular weight of benzol (72 gr.) is 
805,800". Hence he concludes : 
“The six carbon atoms of benzol are united to each other by 
nine single bonds, and the previous assumption of a structure 
of benzol with three single and three double bonds is not sup- 
ported by experiment.” : 
homsen endeavors to prepare the way for the reception 
of this conclusion by emphasizing the statement that: “ The 
great resisting power of benzol militates against the presence of 
multiple bonds.” But although it is true that chlorine or bro- 
mine act on benzol far more feebly than on ethylene or ges 
lene, nevertheless, under no great stress, benzol does yield addi- 
tion products, and there can be no question that the original 
scheme of Kékulé harmonizes more chemical facts than the 
modification of this scheme proposed by Ladenburg. The 
new evidence is very important, but until its bearing has been 
more fully investigated it can not be regarded as conclusive. 
Indeed the interest of this investigation depends not so muc 
on its results as on its method. It is a bold push beyond the 
beaten tracks of science, and although the first results of the 
venture must be accepted with caution, the skill displayed 
ealls forth our admiration and the importance of ‘the methods 
employed justifies this extended notice. 
Tn Sa oa ee Gans ee 
