BETWEEN THE VISCOSITY OE LIQUIDS AND THEIR CHEMICAL NATURE. 97 
coefficients are in reality closely related to chemical nature. If the denominator of 
the left-hand side of the equation t) = 0/(1 + expanded, and if terms 
involving higher powers of t than f' be neglected, we obtain an expression of the 
shape r; = C/(I + + yt^). Such an expression closely reproduces the observed 
values of esters and ethers. This is shown in the following table, which also gives 
the values of ji and y. 
Formula 77 = C (1 yt^). 
P- 
7- 
t. 
j; X 10^ 
(Calc.). 
y X 105 
(Obs.). 
Diff. 
X 105. 
Methyl fonxiate .... 
•01220 
-0-1497 
0 
.30 
318 
.317 
-1 
Ethyl formate .... 
•01224 
0-3086 
50 
299 
299 
0 
Propyl formate .... 
■01375 
0-4519 
80 
280 
280 
0 
Methyl acetate .... 
•01206 
0-3370 
50 
283 
284 
1 
Ethyl acetate. 
•01349 
0-4117 
70 
269 
270 
1 
Propyl acetate .... 
•01514 
0-5423 
100 
252 
250 
-2 
Methyl propionate . 
•01294 
0-3958 
70 
277 
277 
0 
Ethyl propionate 
•01412 
0-4701 
90 
261 
261 
0 
Methyl butyrate .... 
•01485 
0-.5025 
100 
2.54 
256 
2 
Methyl isobutyrate . . . 
•01.386 
0-4657 
90 
256 
256 
0 
Diethyl ether. 
•01074 
0-1828 
30 
214 
212 
-2 
Methyl propyl ether 
•01080 
0-2156 
30 
229 
228 
-1 
Ethyl propyl ether . 
•01170 
0-36.55 
60 
216 
216 
0 
Dipropyl ether .... 
•013.30 
0-4.363 
80 
231 
231 
0 
Methyl isobutyl ether . 
•01154 
0-3345 
50 
230 
2.30 
0 
Ethyl isobutyl ether 
•01292 
0-4119 
80 
209 
210 
1 
The last four columns in the table go to show that even at high temperatures 
where, from its mode of derivation the formula should be least satisfactory, it gives 
values agreeing closely with those observed. Under t is given a temperature near 
the boiling-point of the liquid; under (calc.) and (obs.), the calculated and observed 
values, respectively, of the viscosity-coefficients at t, and the difference between the 
values is given in the last column. It is clear that in all cases a formula of the above 
type will closely reproduce the observed values of 17, and, consequently, and y may 
be regarded as the temperature-coefficients of the different substances. It will be 
seen from the table that the magnitudes of ^ and y are closely related to chemical 
composition. From the fact that the value of n for methyl formate happens to be 
less than unity, the value of y for this ester is negative, and hence its coefficients 
cannot be satisfactorily compared with those of the other substances, as they are all 
positive. Excluding methyl formate, the table shows that in general— 
(1.) In any homologous series y8 and y increase as the molecular weight increases. 
(2.) Of isomeric compounds the iso-compound has the smallest coefficients. 
( 3 .) Ethyl ether, the symmetrical isomer, has smaller coefficients than methyl 
propyl ether. 
MDCCCXCVII.—A. 
o 
