596 
MESSRS. T. E. THORPE AND J. W. RODGER ON THE RELATIONS 
On comparing normal pentane 'vvith isoamylene, loss of hydrogen is attended by a 
slight fall in viscosity of some 15 units. Isoprene and diallyl give numbers which differ 
from those of the corresponding paraffins by about the same amount, some 12 units. 
It is thus evident, that in passing from amylene to isoprene, the effect of loss of 
hydrogen on the viscosity-coefficient is counterbalanced by constitutive influences. 
The effects of constitution are well illustrated by the numbers given by the 
aromatic hydrocarbons which are decidedly larger than those of the corresponding 
paraffins, so that fall in molecular weight appears to be accompanied by rise in 
viscosity. The large difference given by benzene may be attributed to the anomalous 
behaviour exhibited in general by the lowest members of homologous series, to which 
reference has already been made. 
Substitution of Halogen for Hydrogen. 
Bromine for hydrogen. 
Chlorine for hydrogen. 
C^Ho^+^Br. 
Chlormethanes. 
iO. 
Difference. 
>h 
Difference. 
2 
614 
185 
329 
Methylene chloi’ide . 
363 
23 
3 
4.50 
125 
325 
Chloroform .... 
386 
102 
4 
467 
156 
311 
Carbon tetrachloride . 
488 
(Iso) 
On comparing alkylene dibromides with alkyl bromides containing the same number 
of carbon atoms, it is evident that on replacing hydrogen by bromine the viscosity 
coefficient is largely increased. The variation of the effect with increase in molecular 
weight is, however, not regular; this is probably due, as already indicated, to the 
peculiar behaviour of propylene bromide. 
The values for the chlormethanes indicate that, although the effect of substituting 
hydrogen by chlorine is to increase the coefficient, yet the magnitude of the effect 
depends to a great extent on the amount of halogen already present in the molecule. 
Compounds Differing by 1 Carbon Atom. 
Diff. 
'/• 
Diff. 
Tetrachlormethane . 
Tetrachlorethylene . 
488 
881 
-107 
Methyl alcohol .... 
Aldehyde . 
329 
219 
-110 
