xv, 5 Perkins : Rancidity of Coconut Oil 473 
Od and 6 01 show a combined effect of increased initial acidity 
and nonfatty material which is noticeable. 
CONCLUSIONS 
Modifying somewhat the conceptions of rancidity outlined at 
the beginning of this article I submit the following conclusions : 
In the type of rancidity of coconut oil studied the first stage 
is a hydrolysis, the rapidity of which varies with the initial 
acidity and the amount of moisture present. Exclusive of any 
mold action, this hydrolysis may be somewhat accelerated by the 
action of air, light, and a fat-soluble enzyme. 
The second stage of rancidity is an oxidation of the free 
fatty acids. Possibly this involves also the oxidation of un- 
hydrolyzed olein, but the amount of oxidation is dependent on 
the amount of hydrolysis. 
The oxidation is hastened by light and moisture, but light is 
not a necessary condition. 
CHEMICAL METHODS FOR THE MEASUREMENT OF RANCIDITY 
The above conclusions are restricted to the type of rancidity 
studied. Though this appears to be the common type in co- 
conut oil, the possibility of others is not excluded. Walker 21 
describes a “peculiar, pungent, ‘strong’ odor in otherwise pure 
oils.” I have also observed peculiar odors which the remnants 
of samples 3 Sd and 5 Sd, not used for analysis, developed 
during storage for several weeks in a very damp refrigerator. 
Sample 5 Sd, which developed an odor resembling Roquefort 
cheese, was found to contain a slight growth of mold, identified 
by Dr. H. S. Yates, of the Bureau of Science, as a species of 
Torula. Mo microorganism was found in sample 3 Sd, but it 
developed a peculiar, acrid odor. Vfhen both of these odors 
had become readily noticeable little or no change could be 
found, in the oxidizability value, fuchsine aldehyde test, or iodine 
number. The acidity of 3 Sd was 0.87, and that of 5 Sd, 0.95 
per cent, only 0.08 and 0.07, respectively, higher than the values 
previously found. 
Such peculiar types of rancidity indicate that a single chem- 
ical test cannot be expected to enable one to distinguish between 
edible and nonedible coconut oils. In the ordinary type of ran- 
cidity, however, occurring under the conditions of our inves- 
tigation, it appears that the decrease in iodine value, the fuchsine 
aldehyde test, and the oxidizability number give good indica- 
21 Walker, H. S., Philip. Journ. Sci. 1 (1906) 139. 
