BETWEEN THE VISCOSITY OF LIQUIDS AND THEIR CHEMICAL NATURE. 645 
Probably the first three hydrocarbons alone are comparable with one another as the 
xylenes contain two side chains. The general mean value is, however, almost the 
same as that deduced from the first three, as the meta-isomer gives almost the mean 
value, and the values of the ortho- and para-isomers lie to about the same extent on 
either side of the mean. Making due allowance for constitutive effects, it is evident, 
therefore, that the peculiar structure of aromatic compounds exercises an approxi¬ 
mately constant and a most marked effect on their molecular viscosities, which are 
larger by some 244 units than the amounts calculated in the way already indicated. 
The calculated increase, which would be brought about by three double linkages, is 
144 units, so that the observed differences have to be sought for in some additional 
structural effect which acts in the same sense as double linkage inasmuch as it 
increases the molecular viscosity. The whole efiect may at present be termed that 
of the ring-grouping of atoms, no assumption being made as to whether or not 
double linkage participates in bringing it about. 
Thiophen gives the value 151 for the same kind of effect; 
“ Rest.” Ring-grouping. 
Thiophen 699 548 151. 
The effect produced by two double linkages is 96. 
The fundamental constants thus obtained are given below. 
ruNDAME>iTAL Viscosity Constants. (Molecular Viscosity at Slope 'O 4323 .) 
H jdi’ogen. 
H 
44-5 
Carbon . 
C 
.31 
\ / 
Hjdroxy 1-oxygen.C—U—H 
0 
166 
Etber-oxygen.C—0—C 
o< 
58 
Carbonyl-oxygen.C=0 
II 
0 
\/ 
s 
198 
Sulphur.C—S—C 
246 
Chlorine (in monochlorides). 
Cl 
256 
Chlorine (in dichlorides). 
cr 
244 
Bromine (in monobromides). 
Br 
372 
Bromine (in dibromides). 
Br' 
361 
Iodine. 
I 
499 
Iso grouping. 
< 
- 21 
Double linkage. 
(=) 
48 
Ring-grouping. 
® 
244 
