688 
MESSRS. T. E. THORPE AND J. W. RODGER OR THE RELATIORS 
viscosity alters is clifterent for each alcohol and is related to its chemical nature. 
These results are but additional expressions of the marked differences which 
obviously exist between tlie viscosity-curves of the alcohols and those of all the 
other liquids. 
Conclusions relating to Molecular Viscosity Worh at Equal Sloqoe. 
The results here obtained are of precisely the same nature as those discussed under 
molecular viscosity. More detail has been given to show that the substances 
which give deviations from the calculated values fall into two classes, In the first 
the deviations are to be attributed to chemical constitution, as similar disturbinof 
effects may be detected in the magnitudes of other physical properties which do not 
seem to be affected by molecular complexity. In the second are those substances 
like the acids, water, and the alcohols, for which the disturbing factor is, no doubt, 
molecular complexity, the effect produced in this way, in the case of the alcohols, 
being dependent upon their chemical nature. 
Generality oe the Re.sults Obtained at Equal Slope. 
One of the most important points which has to be discussed in connection with any 
physico-cliemical investigation is the question of the generality of the results. Will 
the relationships obtained at one series of comparable temperatures be the same at 
any other series chosen according to the same system, but having different magnitudes 
from those first employed ? For example, will relations betw^een specific moleculai’- 
volunie measured at the ordinary boiling-point be the same at other temperatures 
of equal vapour pressure ? 
In the case of viscosity the question is : Are the results obtained independent of 
the magnitude of the slope ? It has already been showui that on comparing as many 
liquids as could be compared at slopes ‘0^,323 and ’0^,987, practically the same results 
are obtained in each case. Instead, however, of testing the question by means of a 
method like the above, wdrich relates to particular cases, it is possible to treat the 
question in a general wmy by employing Slotte’s formula. 
From y = cjia + it follows that — dyjdt, or the slope S, is given by 
nc 
S =-, and 
(« + /)" + ! ’ 
<g'/!'('/! + ]) _ 
c 1 c 
c J ^ + tf ~~ p (« T 0" ’ 
where 
c \i (K+n 
n’‘-, 
