592 
MESSRS. T. E. THORPE AND J. W. RODGER ON THE RELATIONS 
Homologues (continued). 
1 
Difference. 
Acetic anliyclride. 
277 
- (15) 
Propionic anhydride. 
247 
Benzene . 
316 
- 68 
Toluene. 
248 
- 15 
Ethyl benzene. 
233 
jMethyl alcohol. 
329 
112 
Ethyl alcohol. 
441 
22 
Propyl alcohol. 
463 
- 58 
Butyl alcohol. 
405 
' Isopropyl alcohol. 
491 
- 39 
Isobutyl alcohol. 
452 
- 74 
Isoamyl alcohol. 
378 
Triniethyl carbinol. 
566 
- 148 
Dimethyl ethyl carbinol .... 
418 
It is apparent from tlie table that the effect on the viscosity-coefficient of an 
increment of CHg in molecular weight varies from series to series. 
Paraffins .—In this series the viscosity-coefficient is practically the same, both in 
the case of normal and iso-hydrocarbons. Here we have the somewhat striking result 
that the magnitude of the coefficient is practically independent of molecular weight. 
A similar result holds for the two hydrocarbons, isoprene and diallyl, and also 
for the alkyl chlorides, as the viscosity coefficient of propyl chloride, which does not 
occur in the table, is 274. 
In all the other series, with the exception of methylene and ethylene chlorides and 
the alcohols—that is, in the case of the iodides, bromides, sulphides, ketones, acids, 
anhydrides and aromatic hydrocarbons, an increment of CH^ brings about a diminu¬ 
tion in the viscosity coefficient. Moreover, it is the general rule that the diminution 
becomes less and less as the series is ascended. 
In the case of the dichlorides the compound of higher molecular weight has a 
decidedly higher coefficient. This difference is no doubt affected by the same cause 
which brings about the wide separation of the curves of the isomeric dichlorethanes. 
