BETWEEN THE VISCOSITY OF LIQUIDS AND THEIR CHEMICAL NATURE. 567 
viscosity, and thus we have peculiar steep curves indicating at low temperatures values 
for the viscosity coefficient which are enormous when compared with those of, say, 
the paraffins. This rapid increase in the value of the viscosity is, in all probability, 
to be associated with increasing complexity in the molecule of the liquid alcohol, a 
complexity which is probably much greater in the case of the polyhydric alcohols. 
It is further to be noted that the viscosity curves which most closely resemlde 
those of the alcohols are those of water and the fatty acids, and these are just tlie 
liquids which, along with the alcohols, have, on independent grounds, been held to 
consist of complex molecules. There is thus strong support to the idea that large 
values in d-r^ldt are to be ascribed to changes of molecular complexity, and, further, 
that marked change of complexity is exhibited so far as our viscosity observations 
go by only one type of substances, namely, those which, like water, an acid, or an 
alcohol, contain a hydroxyd group. The peculiarities above referred to are thus 
related to the chemical nature of the substances, and comparisons of the curves for 
hydroxy compounds such as water, formic acid, and propyl alcohol with that of 
heptane, all of which substances have boiling points which differ at most by only 4°, 
makes evident at a glance the peculiarity here considered. 
The following tables contain values of the coefficients of viscosity read off at 
intervals of 10° from the curves originally plotted. Besides giving an idea of how the 
viscosity coefficient varies from substance to substance the numbers may serve as data 
for ascertaining, either graphically or by the ordinary interpolation formulas, tlie 
values of the coefficients at particular temperatures :— 
CoEFFiCfENTS OF ViscosiTY (dyiies per sq. centim.). 
Hydrocarbons. 
Paraffins. 
Temp. 
Pentane. 
Hexane. 
Heptane. 
Octane. 
Isopentane 
Isoliexane. ! Isoheptane. 
o 
i 0 
■00283 
•00.3965 
•00519 
•00703 
•00273 
•00371 -00477 
i 10 
•002555 
•00355 
•00460 
•006125 
•00246 
•003325 -00423 
1 20 
•00232 
•00320 
•004105 
•00538 
■00223 
•00.300 -00379 
30 
■00212 
•00290 
■00369 
•004785 
•00204 
■002725 -003415 
40 
•00264 
•00334 
•00428 
•00247 . -00.309 
50 
•00241 
•00303 
■003855 
•002255 -002815 
60 
•00221 
•00276 
•003495 
•00208 -00257 
70 
•00253 
•00318 
, -00235 
80 
•00232 
■002905 
, , 
' -00216 
90 
•00214 
•00266 
•00200 
100 
•002445 
no 
•002255 
1 
120 
•002075 
! 
