102 
DR. T. E. THORPE AND MR. J. W. RODGER ON THE RELATIONS 
In any group of normal isomeric esters, the formate has the largest value of mole¬ 
cular viscosity work (compare ethyl formate with methyl acetate ; propyl formate 
with ethyl acetate). The other members of the group have values which are prac¬ 
tically identical (ethyl acetate 333, methyl propionate 334 ; propyl acetate 408, ethyl 
propionate 407, methyl butyrate 408. Methyl isobutyi’ate follows the general rule 
in giving a smaller value than the method butyrate. 
Values for ether oxygen at temperatures of equal sloiDe have been calculated using 
the values given in our previous paper for CHg and carbonyl oxygen, but it is evident 
that the values afforded by the esters are not independent of molecular weight, as 
they diminish, without exception, as any series of esters is ascended. Moreover, it 
is not possible to allow for the fact already noted that the molecular viscosity of an 
isomeric ester is the smaller the more nearly the number of carbon atoms in the 
acid radicle approximates to the number iii the alcohol radicle. The main result, 
however, comes out as clearly as in the first condition of comparison that ether 
oxygen has invariably an effect on molecular viscosity widely different from the 
effects of hydroxyl oxygen and carbonyl oxygen. Thus, in the case of molecular 
viscosity, the values obtained were— 
Hydroxyl oxygen.166 
Carbonyl oxygen.198 
Ether oxygen.51 
Although these numbers can only be considered as first approximations, they 
clearly indicate, as already stated, that the constitution of oxy-compounds profoundly 
affects their viscosity. 
The following table shows the temperature at which the viscosity curves have the 
slope ‘0^323 :— 
Esters. 
Methyl. 
Ethyl. 
Propyl. 
Eormate .... 
o 
20'7 
3 7° 7 
60° 1 
Acetate .... 
34-7 
49-6 
69-9 
Pi'opioiiate . . . . 
49-7 
62-6 
. . 
Butyrate. 
68'5 
. . 
. . 
Isobutyrate . . . . 
60-7 
• • 
♦ * 
Ethers. 
o 
Methyl pvojjyl.1'6 
Ethyl propyl .22'4 
Dipropyl.45'S 
Diethyl.— 2'7 
Methyl isobutyl.18"7 
Ethyl isohutyl.37'8 
