BETWEEN THE VISCOSITY OF LIQUIDS AND THEIR CHEMICAL NATURE. 583 
values of the coefficients produced by the replacement of hydrogen by bromine is 
made evident. The chlormethanes also indicate that replacement of one atom of 
hydrogen by one atom of chlorine also raises the values of the coefficients ; that the 
increase varies with the amount of chlorine already present in the molecule is shown 
by the large values of the coefficients given by carbon tetrachloride. 
In connection with these substances the large coefficients of the alkylene dibromides 
as compared with those of acetylene dibromide and bromine, of ethylene dichloride as 
compared with ethylidene chloride, and of tetrachlormethane as compared with 
tetrachlorethylene, are noteworthy. 
Isomers .—Normal and iso compounds have coefficients which are almost the same. 
The acids constitute the most marked exception, probably on account of the disturbing 
effect of molecular complexity. 
Of the two isomeric ketones, diethyl ketone, the symmetrical isomer, has the 
smaller coefficients; the opposite conclusion holds in the case of the chlorethanes. 
The values for the isomeric aromatic hydrocarbons clearly indicate the peculiar 
behaviour of ortho-xylene which has considerably larger values than tlie closely 
agreeing numbers given by the other isomers. 
Water. 
The values of the coefficients obtained for w’-ater are as follows :— 
d- 
7- 
t. 
// X 10^ 
(calc.). 
// X 10 5 
(ob.s.). 
Diff, X 105. 
Water .... 
•03580 
■032-253 
100 
263 
283 
20 
The difference between the observed and calculated numbers is greater than that 
given by any of the substances in the preceding tables, and on introducing another 
term into the formula the difference is changed from 20 to — 14, so that little 
advantage is thus derived. The above agreement is sufficiently close to allow /3 and 
y to be regarded as expressing the temperature effect with sufficient accuracy for the 
end at present in view, and the magnitudes of these coefficients are particularly 
interesting. For, although y is smaller than in the case of several of the liquids 
given in the first set of tables, the value of given by w'ater is the largest of any 
yet considered. At low temperatures, temperature has a large effect on the viscosity 
of water; at higher temperatures, however, the effect is relatively smaller than in the 
case of liquids with correspondingly large values of y8. In its behaviour at low 
temperatures, water strongly resembles the acids, and more especially the alcohols, 
and there is little doubt that the peculiarities of ail these liquids are to be ascribed 
to the presence of molecular aggregations. 
