May 25,1914 
Aroma of Hops 
H7 
225 0 C., a considerable amount of esters, however, appearing also in the 
preceding fractions. 
That the fractionation proceeded with fair regularity in each oil is 
shown by the relationship between the ester numbers of each fraction 
and the general direction of the curves, which is the same in all the oils. 
During the three seasons the curves seem to group themselves accord¬ 
ing to the source of the hops, those of the oils which differ most in ester 
content being separate from the others. The course of the curves is 
therefore, in a sense, an indication of the source of the hops. Throughout 
the several seasons the curve of the imported hops is conspicuous by its 
low position as compared with the curves of the oils from the American 
hops. While it can not be stated with certainty that the oil from the 
imported hops would continue to show this low ester content, it is very 
probable that the same differences would continue, since nine samples 
from five successive seasons all yielded oils poorer in esters than the oils 
from the American hops during the same seasons. 
CHEMICAL EXAMINATION OF THE OIL 
FREE ACIDS 
A small amount of free acids is contained in the oil of hops. In order 
to identify, if possible, these free acids, the oil was shaken out with an 
aqueous solution of sodium carbonate. The alkaline liquid was sub¬ 
sequently acidified and distilled with steam. The aqueous distillate, 
which was acid to litmus paper, was neutralized with sodium hydroxid 
and precipitated with silver-nitrate solution. By ignition of the dried 
silver salts, traces of formic and heptoic acids were observed, but the 
bulk of the volatile acids was identified as valerianic acid, 52 per cent 
of silver salt being obtained. (Silver valerianate requires 51.6 per cent 
of silver.) Formic acid was further identified by the formation of a 
silver mirror from ammoniacal silver-nitrate solution and by the reduc¬ 
tion of mercuric chlorid to mercurous chlorid. 
COMBINED ACIDS 
After saponifying a quantity of the oil with alcoholic potassium 
hydroxid, diluting with water, and separating the unsaponified portion 
of the oil, the resulting alkaline liquid was evaporated to a small volume. 
Acidification with sulphuric acid caused the separation of an oily layer 
on the surface of the liquid. The oily acids thus separated had a pro¬ 
nounced odor of some of the higher fatty acids. After separation of the 
oily layer from the aqueous distillate by means of a separatory funnel, 
the distillate was shaken out with ether to remove traces of the insoluble 
fatty acids. The liberation of such a large quantity of oily acids shows 
that the esters of the oil are for the most part in combination with acids 
of a higher molecular weight which are oily in character and are sparingly 
soluble in water. 
