668 
MESSRS. T. E. THORPE AND J. W. RODGER ON THE RELATIONS 
value as that of para-xylene is below it. The differences give a measure of the 
variation in constitution of these substances. In the following table is given the 
comparison of the molecular viscosity work and several other physical properties of 
these isomers :— 
1 
Tilolecular 
viscosity work. 
Critical 
temperatures.* 
Critical 
pressures.* 
Boiling-point. 
! 
! Ortho-xylene .... 
i 
483 
0 
358 
36-9 
O 
144-0 
9 
13 
IT 
5-0 
! Meta-xylene .... 
474 
345 
35-8 
1.39-0 
7 
1 
■8 
•8 
Para-xylene .... 
467 
344 
35-0 
138-2 
Ethyl benzene .... 
475 8 
.346 12 
.38T -1-2 
136-1 7-9 1 
Molecular magnetic 
Specific molecular 
volume at 
boiling-point. 
Molecular 
1 
rotation.-f 
refraction.^ 
Ortho-xylene. 
13-306 
138-2 
36-050 i 
-575 
-1-5 
•444 1 
Meta-xylene. 
12-731 
139-7 
.35-606 
--058 
— -5 
•031 
Para-xylene. 
12-789 
140-2 
35-575 
Ethyl benzene. 
13-327 --021 
138-7 - -5 
35-332 -718 
1 
As regards the metameric xylenes, except in the case of magnetic rotation, the differ¬ 
ences are of the same sign; this, of course, is the result of the fact that the ortho¬ 
isomer has either the largest value, and the meta compound the smallest value, or 
vice versd. The magnetic rotation of the meta isomer is exceptional, and is slightly 
smaller than that of the para isomer. It is also invariably the case that the differ¬ 
ence between the values of the ortho- and meta isomers is larger than the difference 
between the meta- and para isomers. 
The relation in which the magnitude of the value for ethyl benzene stands to those 
of the other compounds varies with the particular property dealt wuth. 
The difference given in the table is that betw^een ethyl benzene and ortho-xylene; 
from the magnitude and sign of this difference as compared wuth those of the other 
differences it is evident that, in the case of molecular viscosity wmrk, critical tem¬ 
perature, and specific molecular volume, the value for ethyl benzene is intermediate 
between those of ortho- and meta-xylenes. 
* Altscitul, ‘ Zeifc. fiir physik. Ckemie,’ 11, 577. 
t Landolt and Jahn, ‘ Zeit, fiir physik. Cheniie,’ 10, 311 (nu formula). 
X SCHONIIOCK, ‘ Zeit. fiir physik. Chemie,’ 11, 75-3. 
