502 
MESSRS. T. E. THORPE AND J. W. RODGER ON THE RELATIONS 
property Jike viscosity will be affected by the p^eneral contour of the moving molecule. 
The Ijenzene molecule differs from those of all its homologues in containing no side 
chains, and since the curves for the isomeric xylenes show that even a difference 
in the position of the side chains exerts a decided effect on the viscosity, the entire 
want of side cliains may be expected to bring about a marked influence. 
The curve for benzene, the initial member of the liomologous series of aromatic 
liydrocarbons, thus resembles formic acid, the initial member of the series of fatty acids, 
in having an anomalous position with respect to that of higher homologues. 
Alcohols. 
El even alcohols were examined, viz,, methyl alcohol, ethyl alcohol, isopropyl alcohol, 
])ropyl alcohol, trimethyl carbinol, isobntyl alcohol, butyl alcohol, di-methyl ethyl 
carbinol, active amyl alcohol, inactive amyl alcohol, and allyl alcohol. Fig. 18 
re]n*esents the results obtained for methyl, ethyl, isopropyl, propyl, isobutyl, butyl 
and allyl alcohols. The scale in this diagram, as in all those relating to the alcohols, 
is two and a half times as close as that usually employed. 
The peculiar character of the alcohol curves is at once evident. Here the tendencv 
of the slope to deviate fi'om the small values which it has in the case of the paraffins 
and their monohalogen derivatives reaches a maximum. Even methyl alcohol, over 
the comparatively short temperature range between 0° and its boiling point, gives 
large values of dr^ldt, the curve being of the same general shape as the high tempera¬ 
ture regions of the curves of the higher alcohols. In the case of isobutyl alcohol, 
for example, the change in viscosity between 0° and 100° is '0751 ; ovmr the same 
temperature range heptane has a viscosity change of '0032, so that the same tempera¬ 
ture change exerts almost twenty-five times as great an effect on the viscosity 
coefficient in the case of the alcohol as it does in the case of the hydrocarbon. 
The continuous curves in the diagram refer to the four lowest members of the series 
of normal alcohols. It will be seen that the curves are disposed in accordance with 
the theoretical molecular weights of the alcohols. There is no anomaly such as that 
which occurs in the case of formic and'acetic acids, although there is every reason to 
believe that molecular grouping takes place in the case of the alcohols just as in the 
case of the acids. 
From Ramsay and Shirlds’ observations on the four normal alcohols at low 
tem]ieratures, methyl alcohol is the most complex, and the complexity steadily 
diminishes with rise in molecular weight, so that in the case of butyl alcohol it is only 
about half what it is in the case of methyl alcohol. Although this is assumed to he 
the case, the molecular weights of the liquid alcohols still follow one another in the 
order of the theoretical molecular weights, so that the disposition of the viscosity 
curves is in conformity witli the weights of the liquid molecules indicated by surfoce- 
eitei gy olisoi’vations. 
