xv. i 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= , 



W 



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, 



