694 
MESSRS. T. E. THORPE AND J. W. RODGER ON THE RELATIONS 
77 at slope -0^987 
rj at slope •0^323 
was 2'24, which is higher than the mean value given by the other licjuids, viz., 2-03. 
Here we again have definite evidence that the alcohols exhibit peculiarities which 
have no existence in the case of the other liquids. Even the acids which, like the 
alcohols, contain molecular aggregates, give no marked indication of exceptional 
behaviour at different slopes. Between the groups of acids and alcohols there must, 
therefore, be a generic difference which may ultimately be related to the fact that for 
an alcohol the HO group, which is the most active part of the molecule so far as vis¬ 
cosity is concerned, is in connection with a saturated “ rest,” whereas, for an acid 
the “ rest ” is unsaturated. 
In the preceding discussion regarding the generality of the results, viscosity coeffi¬ 
cients only have been dealt with ; similar conclusions hold, however, for molecular 
viscosity and molecular viscosity work, as the molecular area and molecular volume vary 
so slowly with temperature as compared with viscosity, and the relations between them 
at the temperatures of equal slope are so nearly independent of the magnitude of the 
slope, that the change in the viscosity coefficient itself need alone be considered. 
Comparisons in which a different Slope is employed for each Liquid. 
If it is eventually established that a formula of the type used by Slotte represents 
the true temperature-function of viscosity, and also that in such a formula n varies 
from liquid to liquid, from what has been said it is evident that comparisons at the 
same slope will not be general, but will vary with the magnitude of the slope. 
Under such conditions it is obvious, therefore, that to obtain general results the 
slope must vary from liquid to liquid, and the following method indicates how the 
question may be approached, the conditions to be fulfilled being :— 
(l.) That the comparisons shall be general. 
(2.) That the results obtained shall be related to the chemical nature of the 
substances. 
(1.) For generality, it has already been shown that the following relation must 
hold 
Now if Sa^, &c., differ from Sb^, &c., that is, if the slope varies from liquid to liquid, 
slopes can be chosen so as to satisfy the above relation in an indefinite number of ways. 
(2.) It appears, however, from all the preceding comparisons that chemical relations 
will only be made evident when the slopes are nearly the same; hence for chemical 
relations Sa,, Sb^, &c., must be approximately equal, and, of course, Sa.,, Sb., &c., must 
be approximately equal. 
If slopes be chosen, therefore, according to some definite system, and fulfilling the 
