BETWEEN THE VISCOSITY OP LIQUIDS AND THEIR CHEMICAL NATURE. 64-3 
Formic acid, the initial member of the series, presents the greatest divergence 
from the mean value, and the numbers on the whole are not so uniform as those 
given in previous comparisons, the average difference from the mean being 16 units. 
It is probable that the cause of these deviations is to be sought in differences in the 
molecular complexity of the acids. 
From the relations 
\ / II II 
0 + 0 = 364 and O = 198 it follows that the value of hydroxyl oxygen may be 
taken as 
\ / 
O = 166. 
Ethel' Oxygen .—The study of several of the physical characters of substances, more 
especially their optical properties, has indicated that an oxygen atom, when linked to 
two carbon atoms, exercises an effect on the magnitude of a physical property which is 
different from that exerted when it is in the condition of carbonyl oxygen or hydroxyl 
oxygen. The number of compounds available to ascertain if such a difference exists 
in the case of the viscosity constants is hardly sufficient to warrant any definite con¬ 
clusion as to the absolute magnitude of the effect so exerted. Using the values of C, 
H, and 0, and the observed numbers for acetic anhydride and ether, the mean value 
58 is obtained for ether oxygen. So far as the data go, it would appear that 
ether oxygen, or oxygen linked to two carbon atoms, which may be represented as 
0<, has an extremely small value as compared with that of oxygen in a carbonyl 
group, or with that of hydroxyl oxygen as deduced from the acids. 
If such differences are confirmed by more numerous observations, viscosity will 
rank as one of the most useful properties in determining the constitution of oxygen 
compounds. The values obtained for oxygen in different conditions are :— 
Carbonyl oxygen 
Hydroxyl oxygen 
Ether oxygen. 
II 
O = 198 
\ / 
O = 166 
0< = 58 
It is, of course, to be remembered here that the value of O as it is derived from the 
acids is no doubt affected by molecular complexity. 
Value of Sulphur. 
Only two compounds are available for the estimation of the atomic value of 
sulphur S which is singly linked to two carbon atoms. 
4x2 
