xv, 5 Perkins : Rancidity of Coconut Oil . 469 
milligrams of oxygen required to oxidize the distillate from 
100 grams of oil, was found by the formula, 
16 ( N—n ) 
0 = , 
in which N is the number of cubic centimeters of KMn0 4 used, 
n the cubic centimeters of KMn0 4 used in blank test, and W the 
weight of sample. 
Duplicates agreed to about 0.4 for values of less than 4. 
Large values sometimes varied as much as three units. 
Odor . — Oils designated by 1 had fresh coconut odors which 
had not, however, quite the intensity of the aroma of a freshly 
prepared pure oil. Oils designated by 2 were difficult to dis- 
tinguish from those in class 1. They had a suggestion of 
staleness, but would not be called rancid. The oils in class 3 
had been almost deodorized; they had lost their fresh coconut 
aroma, but had not acquired more of a stale odor than had those 
in class 2. Samples 2 Sd and 5 Sd were affected in the same 
way, but to a less extent. 
The oils of class 4 were rancid. They varied somewhat 
among themselves, 3 Od and 4 Od being the best, and 6 Od the 
worst; but all possessed a slight odor resembling that of stale 
lard, which distinguished them from classes 1 to 3, but which 
was not so strong as that of any in class 5. The oils of class 
5 had a fairly strong odor of stale lard. 
RELATIVE EFFECT OF RANCIDITY FACTORS 
Initial acidity . — It appears from Table III that under the 
conditions of the experiment a difference between 0.1 per cent 
and 0.37 per cent original acidity had almost as much effect on 
the keeping qualities of the oil as all the other influences com- 
bined. For only one sample of oil A (4 Sd) had an odor pre- 
ferable to that sample of oil B (2 OIB) which was stored under 
the least favorable conditions; and, so far as was known, the 
two oils A and B were practically identical except for their 
initial acidity. 
From the well-known catalytic effect of acids on hydrolysis 
and the instability of free unsaturated acids as compared to 
their glycerides we would expect initial acidity to have a marked 
effect on the formation of more acidity and rancidity, and this 
is generally considered to be the case. The effect here indicated, 
