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quantity of ortho-compound does not increase on rise of temperature, 
but decrease; this nitration is repeated in Prof. HorLEMAN's labora- 
tory, because the presence of dinitro-compounds may possibly give 
rise in this case to comparativély great errors in the analyses. In 
the case of another example that ‘departs from the rule, the quantity 
of para-product in the nitration of benzoic acid and its methyl ester, 
the changes at varying temperature are so slight that the errors of 
observation may even have changed the qualitative conduct. 
Moreover the above consideration establishes the already known 
practical rule that in general it is desirable for the preparation of 
pure substitution products to work at low temperature ; for according 
to the stated rule higher temperature always promotes the formation 
of by-products. 
When we examine what influence the above result exercises on 
our theoretical considerations, we arrive at the following conclusion : 
When a hydrogen atom in the benzene nucleus is replaced by an 
atom or a group of atoms, an intermediate state makes its appearance, 
which is caused by exactly the same atoms for the substitutions at 
all available places in the benzene-nucleus. For instance in the case 
of a nitration the intermediate state is caused by the coincidence of 
the “kritische Räume” of the carbon atom of the nucleus at which 
the substitution takes place, of the hydrogen atom, and of the OH 
and NO, group of the nitric acid molecule, at least when in an 
analogous way as BortzMann ascribes a “kritische Raum” to the 
NO, molecule, we do so tor the groups in question. Then the above 
conclusion would involve that the volumes of the Räume which 
cover each other, do not differ, or only very little for the substitutions 
at the different places, but that the different velocity of substitution 
is caused by the fact that the more distant atoms influence in a 
different way the energy required for the different places. 
2. An entirely different question, which, however, can be brought 
in connection with what precedes, is the following: Is it possible 
when the quantity of the products, which are formed when a 
second substituent is introduced, is known, to calculate that of 
the substances which are formed when a third substituent is 
introduced? In other words is it possible to draw a conclusion from 
the energies required for the introduction of a second substituent, 
about the energy required for the introduction of a third? If e.g. 
we suppose that toluene is nitrated on one side, chlor benzene on 
the other, we know the relative quantity of the nitroproducts formed ; 
if we now nitrate chlor toluene, it is the question whether the quantity 
