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This is the so-called rule of multiplication, which Prof. HOLLEMAN 
{ried to apply for such calculations already before. This rule appeared 
to be in pretty close agreement with the observations fur the nitra- 
tion of the ortho-chlor and ortho-brom benzoie acids; in other cases, 
however, great deviations from the calculations are found. 
Afterwards HuisinGA proposed a “rule of summation’, but this 
too presents satisfactory agreement only in some cases. If we examine 
what relation would have to exist between the energy quantities 
required for substitution to arrive at a rule of summation, this 
relation appears to assume such an intricate form that it cannot be 
accounted for in my opinion from a theoretical point of view. A 
general rule for the calculation of substitution energies at the intro- 
duction of a third substituent from the values of energy which are 
required for the introduction of a second, seems to me impossible 
to find. It may, however, be possible to find a relation between 
analogous substitutions, and this relation might possibly be discovered 
by means of the energy values calculated above. Up to now I have 
however not made an attempt to do so, because the energy values 
on which the above tables are founded, can certainly still be modified 
in the units, and sometimes even in the tens; the extent of these 
modifications, namely, is in the closest relation with the errors of 
observation which may be allowed in the determinations. 
Moreover 1 will finally point out that in this paper I only intend 
to show that the material of facts admits the assumption that the 
substitution entropies are identical for the different places in the 
nucleus. That this is really perfectly true has of course not been 
proved by the test; we can certainly also account for the data by 
means of equations with two constants (equation 4), in which the 
second constant in general possesses a small value. It appears in 
any case that in general the course of this type of reactions is chiefly 
determined by difference of energy, and the difference of entropy 
plays only a secondary part. As I showed at the end of § 1 our 
theoretical considerations about the mechanism of the chemical re- 
actions may be brought into harmony with these results. 
In conclusion | gladly express my cordial thanks to Prof. HOLLEMAN 
for supplying me with the information which I required for the 
foregoing investigation and for his interest in this work. 
