Nov. 24, 1923 
Studies on Rancidity 
349 
IS EPIHYDRIN ALDEHYDE A NORMAL CONSTITUENT OF RANCID FATS? 
In the following discussion the term “substance R” will be employed 
to designate the one or more constituents of rancid fats which, either by 
themselves or together with active oxygen derived from other con¬ 
stituents of the fat, are responsible for the formation of the red color 
that is obtained from rancid fats in the Kreis test. Substance R might, 
then, be either epihydrin aldehyde itself, or some other compound or 
group of compounds, such as acrolein and oleic, acid peroxid, that might 
yield epihydrin aldehyde in presence of concentrated hydrochloric acid. 
Of these alternative possibilities, the former can not for the present be 
proved or disproved experimentally, because of our inadequate knowledge 
of epihydrin aldehyde and its compounds, and our consequent inability 
to separate and identify them under conditions precluding chemical 
change. The latter alternative, on the other hand, presents a problem 
of unknown dimensions, and except for the specific examples mentioned, 
has not been subjected to extended study. 
A number of more or less blind attempts were nevertheless made to 
separate substance R from rancid fats and rancid oleic acid, in the course 
of which a number of interesting observations were made. 
Fractionation of rancid oleic acid. —One hundred cc. of highly 
rancid oleic acid that gave an intense Kreis test were subjected to 
steam distillation, 150 cc. of distillate being collected. The distillate 
gave a negative Kreis test, both in presence and in absence of hydrogen 
peroxid; but when it was shaken with 25 cc. of ether, a concentration 
of the ether-soluble material of the distillate being thereby effected, the 
ether solution gave a distinct, but rather weak, Kreis test. Thus, while 
some of substance R had distilled, by far the larger amount remained in 
the undistilled oleic acid. 
The undistilled oleic acid, which still gave a strong Kreis test, was 
shaken with several volumes of hot water. The aqueous extract, when 
separated, failed to respond to the Kreis test either in presence or absence 
of hydrogen peroxid; but when it was shaken with a little ether the ether 
solution gave a weak Kreis test in absence of hydrogen peroxid and a 
somewhat weaker test in presence of hydrogen peroxid. 
After its extraction with water the separated oleic acid, which still 
gave a strong Kreis test, was dissolved in ether and shaken with con¬ 
centrated hydrochloric acid. The hydrochloric acid layer, when sepa¬ 
rated, gave a strong Kreis test of about the same intensity as that obtained 
from the ethereal layer. When the hydrochloric acid layer was diluted 
with water and shaken with two separate portions of ether, the ether 
extract responded to the Kreis test while the extracted hydrochloric acid 
did not. 
By these operations most of the reactive substance had been recovered 
from the various fractions in ethereal solution. The several ether 
extracts were combined, dried over calcium chlorid, and allowed to 
evaporate at room temperature. The following morning a dark-brown 
oily substance remained. This residue was dissolved in a few cubic 
centimeters of ether and tested with phloroglucin-hydrochloric acid 
both with and without previous addition of hydrogen peroxid. The 
results were at first questionable, but in each case a decided, though 
not an intense, red color developed after short standing. 
Substance R is thus found to be but slightly soluble in water and 
practically nonvolatile with steam; but it is evidently broken down on 
