548 
MESSRS. T. E. THORPE AND J. W. RODGER ON THE RELATIONS 
Mean temp. 
'/■ 
Difference. 
Observed (mean). 
Calculated. 
O 
7-41 
-01810 
•01810 
•00000 
15-31 
-01508 
•01508 
•00000 
22-81 
-0L283 
•01281 
- -00002 
30-50 
•01096 
•01094 
- -00002 
38-05 
•00946 
•00945 
- -00001 
46-36 
•00811 
•00811 
•00000 
54-10 
•00708 
•00708 
•00000 
60-77 
•00633 
•00633 
•00000 
68-86 
•00557 
•00556 
- -00001 
76-81 
•00492 
•00492 
•00000 
84-50 
•00440 
•00440 
•00000 
92-26 
•00394 
•00394 
•00000 
95 24 
•00379 
•00378 
- -00001 
PART III.—DISCUSSION OF RESULTS. 
Introduction. 
Before proceeding to the discussion of the results obtained, it may be advisable to 
indicate briefly the factors upon which the magnitude of the viscosity may probably 
depend. 
Unlike several of the properties which have been investigated from a physico¬ 
chemical point of view, viscosity depends essentially on the forces in play between 
molecules—it is the result of extra-molecular actions. It has loncj been coniectured 
that the fundamental molecules of some liquids, at least, are really congeries of 
gaseous molecules. Naumann, fi’om the boiling-points of isomers; Ramsay and 
Young from the variations of saturated vapour densities; Guy^e and Young from 
critical densities, and others, have given evidence in favour of this conclusion. The 
most significant contribution to the subject, however, was made as long ago as 1886, 
by Eotvos (‘ Wied. Ann.,’ 27, 452). He was able to show that for many liquids the 
rate of change of molecular surface energy with temperature was independent of the 
temperature and of the chemical nature of the liquids ; whereas for other liquids, like 
water, the fatty alcohols and the fatty acids, this was no longer the case. Eotvos 
attempted to show theoretically that to the former class belonged substances for 
which the complexity of the liquid molecule was the same as that of the gaseous 
molecule, while to the latter class belonged substances for which the complexity of the 
liquid molecule was the greater. He also indicated how the degree of complexity at 
any temperature might be ascertained. 
Quite recently, Ramsay and Shields (‘ Phil. Trans.,’ 1893), b}^ means of the principle 
used by Eotvos, have largely supplemented the observations of the Hungarian 
