94 
DR. T. E. THORPE AND MR. .T. W. RODGER ON THE RELATIONS 
left of that of methyl butyrate—it is, indeed, to the left of those of any of its isomers. 
The curves of methyl butyrate and propyl acetate are interesting inasmuch as, 
contrary to what holds in most series of related substances, they cut one another. 
At 0° the coefficient of the acetate is the larger by about 1'4 per cent., while at 100° 
the coefficient of the butyrate is the larger by about 2'4 per cent. 
Ethers. 
Five ethers have been dealt with in the previous part of this paper. The curves 
obtained are given in fig. 2, which also contains, for the sake of comparison, the curve 
for ethyl ether. .As in the case of the esters, the effect of temperature on viscosity 
is small, and does not vary much as the temperature alters. 
Fig. 2. 
On passing along the diagram from below upwards the order of the curves is ; 
diethyl ether, methyl j^ropyl ether, methyl isobutyl ether, ethyl propyl ether, ethjd 
isobutyl ether, and dipropyl ether. They follow, therefore, in the order of the mole¬ 
cular weights of the compounds. 
As I’egards the curves of isomers, it is noticeable that diethyl ether, the symmetrical 
isomer, has at all temperatures a lower viscosity than methyl propyl ether. 
Again, as in the case of esters, of the isomeric ethers the iso-compound has the 
lowest viscosity ; the curve for methyl isobutyl ether lies below that of ethyl propyl 
ether, and the curve for ethyl isobutyl ether lies below that of the symmetrical isomer 
dipropyl ether. This last comparison is interesting as showing that the presence of 
an iso-linkage has a more important effect in reducing the viscosity than the mere 
symmetry of the molecule. 
In our previous paper an effect of symmetry similar to that which holds for the 
esters and ethers was shown by diethyl and methyl propyl ketones; the symmetrical 
isomer had the lowest viscosity. 
