136 
value. However, on heating in a sealed tube, considerable alteration took 
place, as is shown in the following: Samples from No. “B” and from that 
portion of No. 11 which had been exposed to sunlight were heated in 
sealed tubes at about 160° for ten hours. “B” changed in percentage 
of free acid from 0.06 to 0.90, but was unchanged in color, odor, or taste. 
“11” rose from 0.24 per cent to 2.05 per cent under the same conditions, 
and possessed a very disagreeable odor and a nauseating taste. It also 
showed a considerable increase in color, probably due to decomposed 
albumin, ete. The change taking place in the sample was demonstrated 
to be a simple hydrolysis by heat and moisture. In the next experiment, 
both “B” and “11” (original samples) were dried very carefully by 
passing through them a current of dry air for seven hours at 100°; 10 
cubic centimeters each of the dry oils were then sealed in glass tubes and 
heated at about 160° for ten hours. For comparison, two more tubes 
of oil were subjected to the same conditions, one containing 10 cubic 
centimeters of sample 11 (undried), the other 10 cubic centimeters of 
the dried oil **B” plus 3 drops of water. 
Oil Before After 
2 heating. | heating. 
OR a ee ead eae. 0.07 0,09 
Ea Al) Coaneckgadaddans «cebkamiece< 0. 07 14.8 
YU | gees Meare fr occ ee ee 0.18 0,19 
TS) Orleite ls acl o con ene 0.18 | 0. 46 
In neither of the samples marked “B” was a bad odor or any color 
produced, though the hydrolyzed sample was slightly unpleasant to the 
taste, owing to the large amount of free acid present. However, both the 
similarly treated tubes containing oil No. 11, in spite of their low acid 
value, were decidedly disagreeable to the taste and smell and presented a 
decomposed appearance. 
FACTORS WHICH CAUSE RANCIDITY IN OIL, 
The average person, if asked to judge of the quality of these four 
heated oils by the sense of taste and smell alone, would almost invariably 
say that both samples of oil No. 11 were “rancid” and that the other two 
were fairly pure, whereas, judging from the amount of free acid present, 
one might consider “ B + aq.” as the only sample containing a marked 
amount of rancidity. From the above it is evident that rancidity and 
free acid are not by any means synonymous and that the cause of the 
former must be sought elsewhere than in the percentage of the latter. 
Lewkowitsch applies the term “rancidity” only to those fats which contain 
an excess of free fatty acids due to the action of air. 
Alder Wright gives a résumé of the work done on this subject and concludes 
* Alder Wright: Fixed Oils, Fats, Butters, and Waxes, second edition (1903), 
168. 
