o-Cresol *) M-R,. = 32,52 o-Chloraniline?) M-R. = 35,46 
m-Cresol 7 32.56 m-Chloraniline 5 35,55 
p-Cresol E 32,57 
The molecular refractions of isomeric compounds are almost the 
same, if the absorption bands are situated far outside the visible 
part of the spectrum. 
If however these bands are situated very near to or in the visible 
part of the spectrum, as is the case with all nitro-anilines and 
-toluidines examined so far, then the molecular refractions show 
great differences. 
So it is evident that in the last mentioned substances the value 
of the molecular-refraction depends on the presence of absorption 
bands in the neighbourhood of the kind of light chosen for the 
determination of the refraction. 
In connection with this we call attention to the molecular refrac- 
tions of the 2.3- and 2.5.dinitro-dimethyl-p-toluidine and the respective 
nifrosamines, 
2.3, Dinitro-dimetbyl-p-toluidine. M-R. = 59,6 | 
és i 5 A= 15 
2.9. EE) LE) EE) EE) EE) 61,4 
2.3. Dinitro-tolyl-methyl-nitrosamine. en 56,9 HE 
2.5. 29 ” EE) LE) LE) 57,4 Pips 
The difference in molecular refraction of the two strongly coloured 
dinitro-dimethyl-p-toluidines has almost disappeared, after substitution 
of a NO-group for a CH, group, in consequence of which almost 
colourless nitrosamines are formed. 
Besides the molecular refractions of these nitrosamines-are much 
smaller than those of the dimethyl compounds. 
A careful examination of the molecular-refraction and absorption 
curve brings the following relations to light, 
As has already been observed the molecular refraction is to a 
high degree dependent on the position of the nitro-group with respect 
to the amino-group. If we arrange isomerides according to the value 
of their molecular refractions and if we act in like manner with 
the homologues of these isomerides, then in both cases we get the, 
same succession save a single exception which is easy to explain. 
Thus we have: 
M.-R. of p-nitro-aniline > M.-R. of m-nitro-aniline. 
M.-R. of p-nitro-dimethyl-aniline > M.-R, of m-nitro-dimethyl-aniline. 
1) EYKMAN, Rec. 12, 177 (1893). 
*) See note 5 p. 573 
