BETWEEN THE VISCOSITY OE LIQUIDS, AND THEIR CHEMICAL NATURE. 99 
Of the isomeric butyrates the iso-compound, in conformity with the general rule 
(compare p. 599, Part I.), has the larger coefficient. The ethers, however, afford an 
additional instance of an homologous series (compare pp. 590 and 592, Part 1.) 
in which the different members have nearly the same viscosity at the boiling-point. 
On comparing the values for diethyl ether and methyl propyl ether the symmetrical 
compound, as in the case of the ketones (compare pp. 599 and 605, Part I.) has the 
lower viscosity. 
The exceptional character of the formates is no doubt connected with the excep¬ 
tional behaviour of formic acid, the molecular viscosity of which is abnormally large, 
greater, indeed, than that of acetic acid (compare pp. 591 and 610, Part L). 
In our previous paper we showed that the values of CHg varied in different series, 
but that on making allowance for the influence of molecular complexity and of 
differences in chemical constitution (compare p. 606, Part I.), we concluded that the 
probable value of the effect of CH, on the molecular viscosity of comparable liquids 
was 62. It is satisfactory to find that this number is almost identical with the mean 
value now given by the esters and ethers, as derived from the thirteen available 
differences, viz., 61 ±6. 
As regards molecular viscosity work it will be seen that the differences between 
the formates and acetates are nearly constant and in mean about 25 ; whilst the 
remaining differences given by the esters are also fairly uniform, viz., 46, the mean 
value given by the ethers is 50. The general mean, 48 3, corresponds with that 
arrived at in our former paper, viz., 47. 
llie Value of Ether. Oxygen .—the effect of CHo on the molecular viscosity 
and molecular viscosity wmrk of the esters and ethers is the same as the value 
adopted in our previous paper, we may assume that the values of the atomic con¬ 
stants of carbon and hydrogen there used also apply in the case of the esters and 
ethers. If we further assume that the value of carbonyl oxygen is the same for the 
ethers as for the ketones, we have all the data for calculating the value of ether 
oxygens. The results are given in the following tables :— 
Esters. 
C„H2„00<. 
(Ob.s.). 
II 
CHIo^D. 
(Calc.). 
0<. 
Methyl formate. 
492 
372 
120 
Ethyl formate. 
555 
434 
121 
Pi'opyl foi’mate ... 
620 
496 
124 
il ethyl acetate. 
508 
434 
74 
Ethyl acetate. 
567 
496 
71 
Propyl acetate. 
626 
558 
68 
Methyl propionate .... 
565 
496 
69 
Ethyl propionate .... 
614 
5.58 
56 
Methyl butyrate. 
630 
5.58 
72 
diethyl isohutyrate .... 
633 
573 
60 
o 2 
