606 
MESSRS. T. E. THORPE AND J. W. RODGER ON THE RELATIONS 
in chemical composition corresponds with an increase in molecular viscosity. This 
increase is, however, far from being constant, even in the same series. 
(2.) With the above exceptions, it is also apparent that the corresponding 
compound having the highest molecular weight has the highest molecular viscosity, 
and the differences between the members of two corresponding series are fairly constant. 
(3.) The relationships shown in the other tables are substantially of the same 
nature as those given by the viscosity coefficients. 
The comparisons which give the largest deviations from regularity contain those 
substances which have already been shown to exhibit a peculiar behaviour, namely, 
the alcohols, acids, propylene dibromide, ethylene dichloride, &c. 
In order to give some idea of how far molecular viscosity at the boiling-point is 
quantitatively connected with chemical nature, attempts were made by the method 
given in detail at a later stage to calculate the probable partial effects of the atoms 
on the molecular viscosity. Values were also assigned to the effect of the iso 
grouping of atoms, the double linkage of carbon atoms, and the ring grouping. The 
values thus obtained are given in the following table :— 
Fundamental Viscosity Constants (Molecular Viscosity at the Boiling-point.) 
Hydrogen. 
H 
80 
Carbon. 
C 
- 98 
Hydroxyl-oxygen. 
. C—0—H 
196 
Ether-oxygen. 
. C—0—C 
0< 
35 
Carbonyl-oxygen. 
. c—0 
il 
0 
248 
Sulphur.. . . 
. C—S—C 
155 
Chlorine. 
Cl 
284 
Bromine (in monobromides) 
Br 
420 
Bromine (in dibromides) . 
Br' 
479 
Iodine. 
I 
520 
Iso groiiping. 
< 
15 
Double linkage. 
(=) 
113 
Ring- grouping. 
® 
610 
The main points to be considered in connection with the meaning to be attached to 
fundamental viscosity constants in general, may be introduced here. 
As has already been stated, viscosity may be taken as a measure of the attractive 
