BETWEEN. THE VISCOSITY OF LIQUIDS AND THEIR CHEMICAL NATURE. 669 
In the case of critical pressure and magnetic rotation ethyl benzene has the largest, 
and in the case of boiling-point and molecular refraction the smallest, value of all the 
isomers. The relations between the magnitudes of the viscosity constants of these 
substances is thus in harmony with their other physical properties. 
In what follows the observed values of substances which are not included in the 
preceding table, and which were not employed in deducing the fundamental constants, 
are compared with the values given by the other substances. 
Amylene .—Assuming that the substance employed is a straight chain compound 
containing one double linkage, 
the calculated value is 305 1 
> Difference . 2. 
the value found is 307 
On Dr. Perkin’s authority, however, the sample is tri-methyl ethylene, and if, in 
addition to a double linkage, an iso linkage be taken to exist in the molecule, the 
calculated value is modified to 297, and the difference raised to 10 , or about 3 per 
cent. This difference is somewhat greater than those usually found in the preceding 
table, and it is noteworthy that Dr. Perkin found that the magnetic rotation of this 
sample was anomalous (compare ‘ Journ. Chem. Soc.,’ 45, p. 561, 1884). 
It may also be pointed out that this substance is the only one examined in which 
an iso linkage is associated with a double linked carbon atom; of all the substances 
investigated by us it alone contains the group 
^ > CH = C. 
The same remarks apply in the case of molecular viscosity. 
Chlormet]lanes .—In deducing the values of the fundamental constants it has been 
established that if the values of carbon and hydrogen be taken as constant, the value 
of the halogen in a dihalogen compound is invariably lower than the value in a mono¬ 
halogen compound. 
Prom the values affi)rded by the chlormethanes it would appear that a similar 
decrease still takes place in the case of tri- and tetra-halogen compounds. In 
order to indicate this change in the value of the halogen, we give in the following 
table the observed values of the chlormethanes and the values calculated by using the 
value possessed by chlorine in monochlorides. 
t)(P (observed). 
7 # (calculated). 
Difference. 
Methylene chloride .... 
241 
258 
-17 
Chloroform. 
.328 
381 
-53 
Carbon tetrachloride .... 
406 
504 
-98 
