596 
ether, the first fractions are still essentially the isomer 1,2,5; but 
at last, a fraction was obtained, melting at 70°—75°, whose melting 
point rose to 95°, when it was mixed with an equal quantity of 
the acetaminocompound 1,24. Though the latter could not be isolated 
in a perfectly pure state from the mixture, this test proves nevertheless 
with certainty its presence. This was still corroborated by treating 
an artificial mixture of the four isomers, containing them in nearly 
the same proportion as the nitration product (see below) in the same 
way; it showed quite the same peculiarities and neither from this 
mixture could the isomer 1,2,4 be isolated perfectly pure. The pro- 
portions of solubility of this compound and of many of its deriva- 
tives in comparison with those of the isomers are too unfavourable 
to allow its extraction. 
After having proved that really the four possible nitro-o-chloroto- 
luenes occtir in the nitration product of o-chlorotoluene, we proceeded 
to estimate the relative quantities in which these isomers are formed. 
The nitration itself was executed as follows. To 10 gr. o-chlorotoluene 
was dropped 40 ers. of nitric acid sp.gr. 1.52 while stirring mechani- 
cally; the temperature being kept between — 1° and + 1°. 
For the analysis of the nitration product, the melting point method 
was applied in ihe medifieation described by Varrrox. When looking at 
the six binary melting curves, which are possible with the four isomeric 
nitro-o-chlorotoluenes, one perceives, that these curves coincide over a 
considerable range of temperature. For instance, considering the 
binary curves for 1, 2,5 -+ 1, 2, 3 and 1, 2,5-+-1, 2,4, we see that 
the branches at the side of the isomer 1, 2,5 coincide practically, 
and it is the same in the other cases. We have then to do with 
so called “ideal melting curves”; they show the property that the 
lowering of the freezing point, say of the isomer 1, 2,5, is the same 
for the addition of a certain percentage of any of the other isomers 
or of mixtures of them, unless their sum comes again to the same 
percentage. 
Wishing now to determine quantitatively one of the isomers, say 
1.2,5, we add to a known weight of the nitration product so much 
of that isomer (of course also weighed) that it crystallizes at the 
first freezing point of the mixture and we determine this point. We find 
then with the aid of one of the melting-point curves the total amount 
of this isomer in the mixture and it is now only a simple arithmetic 
operation to calculate the amount of the isomer in the original 
nitration product. In the same way, the quantity of the other 
isomers is determined. 
By this method, we found that the nitration product of o-chloro- 
