36 o 
Journal of Agricultural Research voi. xxvi, No. 8 
On theoretical grounds, oleic acid peroxid, azelaic half aldehyde, and 
ketoxystearic acid also seem to be eliminated; while glyceric aldehyde 
is eliminated on the basis of statements in the literature. 
5. The color obtained in the Kreis test on rancid fats has been found 
to be spectroscopically identical with that obtained in the Kreis test on 
mixtures of acrolein and hydrogen peroxid. 
6. The compound that results from the interaction of acrolein and 
hydrogen peroxid, that responds to the Kreis test, and that has been 
referred to in this paper as substance K, has been identified as epihydrin 
aldehyde. It could not be isolated, however, because of its instability, 
but its diethylacetal has been synthesized. 
7. The constituent of rancid fats that causes the Kreis test is not 
free epihydrin aldehyde, but it is certain that it gives rise to epihydrin 
aldehyde when the rancid fat containing it is brought into contact with 
the concentrated hydrochloric acid used in the Kreis test. There is 
some reason for supposing that substance R may be an acetal of epihydrin 
aldehyde. 
8. A positive reaction in the Kreis test, when the test is performed in 
the usual manner, is not always a reliable indication of rancidity in fats. 
A large number of compounds react with phloroglucin-hydrochloric acid 
to give a red color that, to the unaided eye, is indistinguishable from the 
color obtained with rancid fats. Such a reaction is notoriously given 
by many samples of nonrancid cottonseed oil. When the test is modified 
in such manner that the color obtained is examined spectroscopically, 
however, the modified test becomes a reliable index of the rancid condition. 
9. A mechanism has been provisionally suggested to explain the forma¬ 
tion of epihydrin aldehyde or its precursors in the atmospheric oxidation 
of oleic acid. This mechanism also provides for the formation of heptylic 
aldehyde and of such other fatty aldehydes as other workers have isolated 
from rancid fats. 
LITERATURE CITED 
( 1 ) Arppe, A. E. 
1862. ueber die azelainsAure. In Liebig’s Ann. Chem. Bd. 124, p. 86-98. 
(2) Beilstein, F. K. 
1918-20. handbuch der organischen chemie. Aufl. 4. Bd. x-2. Berlin. 
(3) Bergh, Gustaf Fr. 
1909. uber die darstellung des acroleins. In Jour. Prakt. Chem., N. F., 
Bd. 79, p. 351-357, illus. Bibliographical footnotes. 
(4) BromEis, C. 
1840. UEBER DIE EINWIRKUNG DER SALPETERSAURE AUP STEARINSAURE UND 
OELSAURE UND DIE HIERDURCH ERZEUGTEN PRODUKTE. In Liebig’s 
Ann. Chem., Bd. 35, p. 86-112. 
(5) Browne, C. A., Jr. 
1899. A CONTRIBUTION TO THE CHEMISTRY OP BUTTER-PAT. III. THE CHEM¬ 
ISTRY op rancidity in butter-pat. In Jour. Amer. Chem. Soc., 
v. 21, p. 975-994. Bibliographical footnotes. 
(6) Carette, H. 
1886. sur l’oxydation des acides des graisses. In Compt. Rend. Acad. 
Sci. [Paris], t. 102, p. 692-693. 
(7) Claisen, L. 
1903. ZUR KENNTNISS DES PROPARGYLALDEHYDS UND DES PHENYLPROPARGYL- 
aldEhyds. In Ber. Deut. Chem. Gesell., Jahrg. 36, p. 3664-3673. 
Bibliographical footnotes. 
(8 ) Duclaux, E. 
1887. sur la migration DES matures grasses. In Ann. Inst. Pasteur, 
ann. 1, p. 347-355- 
(9) Durrans, Thomas H. 
1919. THE RELATIONSHIP BETWEEN ODOUR AND CHEMICAL CONSTITUTION. In 
Perfumery and Essential Oil Rec., v. 10, p. 104-136. 
