1125 
Probably the deviation remains within the errors of observation 
also here. This supposition seems not too hazardous when the results 
are considered which were obtained in the nitration of the methyl 
ester of benzoic acid, where very probably in the nitration an error 
oceurs at 0°, which is greater than the above deviations. Prof. Houur- 
MAN informed me that he too considered the agreement in the tables 
as very satisfactory. 
The above test, therefore, really leads to the conclusion that the 
substitutions in the benzene nucleus can be satisfactorily accounted 
for up to now by one single constant, the difference of energy for 
substitution at the different places in the nucleus. If there were only 
one example known where the errors of observation were undoubt- 
edly’ smaller than the deviation from the theoretically calculated 
value, the originally proposed hypothesis would have to be rejected ; 
so it will have to appear from the continued investigation whether 
really all the examples without exception conform to the rule, for 
which no exceptions have been found as vet. 
Equations 3 and 5 accordingly, account for the facts which are 
known up to now. If we now compare the two equations, we come 
to the following conclusion: The second members of the two 
equations have always opposed signs; if therefore in equation 5a 
he, Sh i.e. if on substitution more meta- than orthoderivative is 
formed, then &  —e, is negative. 
k, 
dln — 
[t then follows from equation 3a that the value of ———" 
E 
tive. We can express this generally as follows : : 
iS posi- 
The quantity of the product which is formed to a smaller degree, 
increases relatively on rise of temperature. 
In this we should bear in mind that to decide whether a product 
is formed: in a smaller quantity, if is necessary to divide the quan- 
tities formed by the value that indicates the number of equivalent 
places in the nucleus. Thus the nitration of toluene furnishes 
seemingly an exception, as seemingly the quantity of ortho is greater 
than the quantity of para-nitrotoluene. If however, it is borne in 
mind that in this substitution there are two ortho-places available 
to one para-place, and that therefore para and not ortho is the 
product that is formed in greater gaat ity, the stated rule appears 
to be valid also here. 
As far as I am aware there are no exceptions to this rule either. 
Only the nitration of iodo-benzene does not follow it, as here the 
