148 
Journal of Agricultural Research 
Vol. II, No. 3 
After neutralization and fractional precipitation with silver-nitrate 
solution, the aqueous distillate representing the soluble volatile com¬ 
bined acids produced small amounts of silver salts which contained 66 
and 71 per cent of silver, respectively. The combined soluble acids 
therefore consisted largely of formic acid with a trace of acetic acid. 
The oily acids previously mentioned, which represented the bulk of the 
combined acids, corresponded to 5 per cent of the total oil saponified. A 
small amount of the oily acids, which had a most unpleasant, repulsive 
odor, was neutralized with potassium-hydroxid solution. The neutralized 
solution was then precipitated fractionally with silver-nitrate solution. 
The first two fractions precipitated, which were the smallest and repre¬ 
sented the most insoluble salts, yielded 38.5 and 39.2 per cent of silver, 
corresponding to decylic (caprinic) acid. (Silver salt of decylic acid 
contains 38.6 per cent of silver.) The third and fourth fractions of silver 
salts assayed 40.3 and 40.9 per cent of silver. These results correspond 
very closely to nonoic (pelargonic) acid, whose silver salt contains theo¬ 
retically 40.7 per cent of silver. Fractions 5 and 6, containing 41.6 and 
44 per cent of silver, respectively, had perhaps traces of the preceding 
nonoic and succeeding lower acids. In all probability a portion of these 
fractions consisted of octoic (caprylic) acid, which theoretically requires 
42.9 per cent of silver. The final fractions both gave 46 per cent of 
silver, which corresponds well with heptoic (oenanthylic) acid. This 
acid contains theoretically 45.5 per cent of silver. Based on the total 
weight of all precipitates, it appears that the oily acids in combination 
as the esters in the oil of hops consist of about equal proportions of 
heptoic, octoic, and nonoic acids, with a somewhat smaller content of 
decylic acid. 
Analyzing the fractions of a fractionated oil in another experiment for 
both free and combined acids, these results were verified in every respect, 
and additional acids were identified. In the lower boiling fractions 
butyric acid was identified among the free acids in addition to the formic, 
valerianic, and heptoic acids previously mentioned. 
Heptoic, octoic, and nonoic acids were formed in the free state in the 
higher boiling fractions, due probably to the splitting oil of these acids 
from the esters at the high heat of distillation. The insoluble acids in 
all the fractions consisted largely of heptoic and nonoic acids, with some 
octoic acid, the highest boiling fractions containing two higher acids, 
decylic and undecylic. 
FRACTIONATION OF SAPONIFIED OIL 
The saponified oil remaining after separation of the acids was twice 
fractionated with a 3-bulb Ladenburg flask, and the results are given in 
Table VIII. 
