656 
MESSRS. T. E. THORPE AND J. W. RODGER ON THE RELATIONS 
a double linkage correspond to a definite change in molecular viscosity work 
of some 29 units. 
Isologous Hydrocarbons. 
n. 
Difference. 
C„H.3„. 
' 
C.H 
2«-6- 
Difference. 
}]d?. 
Difference. 
rjd^. 
5 
329 
21 
308 
45 
284 i 
6 
415 
59 
356 
101 
314 
7 
495 
« • 
99 
396 
8 
574 
• • 
99 
475 
Loss of hydrogen is accompanied by a fall in the value of the molecular viscosity 
^vork. A benzene hydrocarbon has a value which is invariably lower by almost 
100 units than that of the normal paraffin containing the same number of carbon atoms. 
The values for isoprene and diallyl are some 52 units lower than those of the corre¬ 
sponding paraffins, and that of iso-amylene is some 21 units lower than that of normal 
pentane. 
It is noteworthy that these numbers, 100, 52, and 21 are, in the same sense as, 
although not strictly proportional to, the corresponding differences in chemical compo¬ 
sition, viz., Hg, H^, and Ho. 
Substitution of Halogen for Hydrogen. 
n. 
C.Ho^Bro. 
Difference. 
C^HoM+iBr. 
Chlormetlianes. 
Difference. 
>ld\ 
,)d^. 
2 
450 
168 
282 
Methylene chloride . 
241 
87 
3 
526 
173 
353 
Chloroform. 
328 
78 
4 (Iso.) 
614 
181 
433 
Carbon tetrachloride. 
406 
The mean increase in molecular viscosity work for the change of a monobromide 
into a dibromide is 174 : the increase, however, tends to become greater the higher 
the molecular weight. 
As in the case of molecular viscosity the effect of substituting H by Cl in a chlor- 
methane is smaller the larger the amount of chlorine in the molecule. 
