35 2 
Journal of Agricultural Research 
Vol. XXVI, No. 8 
(b) The residual lard from the preceding experiment, containing the 
epihydrin acetal, was shaken with an equal quantity of cold water. 
After the aqueous extract had separated, it was drawn off and filtered. 
When 5 cc. of the aqueous extract was treated with a few drops of con¬ 
centrated hydrochloric acid and a few crystals of phloroglucin, a clear, 
though not intense, red color was obtained, similar to that obtained 
from slightly rancid fats in the Kreis test. 
(c) About 25 cc. of a strongly rancid lard were melted and shaken 
with about 10 cc. of water. After the aqueous extract had separated, 
it was drawn off and filtered. When 5 cc. of the extract were treated 
with a few drops of concentrated hydrochloric acid and a few crystals of 
phloroglucin, a distinct, but somewhat weak, red color was obtained, 
which was similar in all respects to that which was obtained in the same 
manner from the water extract of the sweet lard to which epihydrin 
aldehyde diethylacetal had been added. 
It thus appears that substance R and epihydrin aldehyde diethylacetal 
are alike in their solubilities in water and in fat, and the possibility is 
suggested that substance R may be one of the acetals of epihydrin 
aldehyde. 
While it has not been possible to isolate substance R, or to establish 
its identity, the foregoing experiments have indicated that it is but 
slightly soluble in water, that it is practically nonvolatile with steam, 
that it is slightly volatile at pressures of from 0.2 to 0.5 mm. and a tem¬ 
perature of ioo° C., and that it is gradually decomposed at higher tem¬ 
peratures, at least in presence of rancid fats. Substance R, therefore, 
can not contain free acrolein, which is readily volatile at low temperatures 
and quite soluble in water; presumably it is not free epihydrin aldehyde, 
which would be expected to resemble acrolein in these respects. 
At the same time, substance R resembles epihydrin aldehyde diethyl¬ 
acetal as regards its solubility in fats and in water and in the ability 
of its dilute aqueous solution to react in the characteristic manner with 
phloroglucin in the presence of minimal amounts of acid. These facts 
suggest that substance R may contain the epihydrin aldehyde radical 
intact, and may be constituted as an acetal, possibly the glyceryl acetal, 
of epihydrin aldehyde. 
spectrophotometric observations 
It remains to describe the results of the spectrophotometric color 
comparisons, by means of which we have established the identity of the 
phloroglucids obtained from substance K, epihydrin aldehyde diethyl¬ 
acetal, and rancid fats, respectively. For a discussion of the principles 
underlying the spectrophotometric method, and a description of the 
instruments employed, the reader is referred to standard text books on 
the subject. The author is indebted to Dr. H. Wales, of the Bureau of 
Chemistry, who made the present examinations by means of an instru¬ 
ment that employs rotating nicol prisms for varying the intensity of the 
normal spectrum with which the absorption spectrum is compared. 
The several solutions examined were prepared as follows: 
(a) From acrolein-hydrogen peroxid .—A dilute aqueous solution of 
acrolein was treated with an excess of hydrogen peroxid, and a few 
drops of the mixture were treated in a separatory funnel with about 10 
