May 25, 1914 
Aroma of Hops 
135 
gravity from fraction to fraction, as observed in the table, may be con¬ 
strued to mean that a fairly good separation of the denser compounds 
has taken place. The fractions of the lowest specific gravity in all cases 
were those boiling below 185° C. This portion of the oil should contain 
the terpenic constituents if present. Fractions 1,2, and 3 did not differ 
greatly, from each other through the four seasons, thus indicating a 
similar composition of the oils. The specific gravity of the oils from the 
cold-storage samples was greatly different from that of the other oils, 
being higher in all cases than in the oils from the fresh hops. The specific 
gravity of fractions 4, 5, and 6 increased very much in the sequence in 
which they were distilled, comparing very favorably, however, in the 
different oils. The oxygenated constituents, if present in the oil, would 
possibly be found largely in fractions 4 and 5, while fractions 6 and 7 
should contain sesquiterpene constituents. Fraction 7 showed a decrease 
in specific gravity, due probably to partial decomposition at the high 
temperature at which it was distilled. 
Curves of the specific gravity were not drawn because of the similarity 
in the various fractions, the same general course being evident in each oil. 
In general, the table of results shows that the fractionation of each oil 
proceeded about the same with regard to the nature of the constituents 
which distilled over. Although the specific gravities corresponded very 
closely, it is not necessarily inferred that the oils are alike in composition. 
The difference may be quantitative rather than qualitative, the size of 
the fractions determining the quantitative composition of the oils. 
OPTICAL ROTATION 
The value of the property of optical rotation, though important in 
most volatile oils, is perhaps lessened when applied to oil of hops, since 
its constituents are more or less inactive or only slightly active. The 
rotatory power of each fraction of the oils was carefully determined, 
and as it was low it was expressed in minutes rather than degrees. 
The results were tabulated for each season (Table VI) and curves 
were drawn to facilitate the comparison (figs. 6, 7, 8, and 9). 
Table VI .—Specific rotation of fractions of hop oils distilled for the years 1906 to 190Q, 
inclusive . 
1906 CROP. 
Source of hops. 
Fraction 
1,165° to 
185* C. 
Fraction 
a, 185° to 
2os* C. 
Fraction 
3, 205 0 to 
225“ C. 
Fraction 
4, 225° to 
245 *C. 
Fraction 
St 24s 0 to 
260* c. 
Fraction 
6, 260° to 
275 ° C. 
Minutes. 
Minutes. 
Minutes. 
Minutes. 
Minutes. 
Minutes. 
Oregon. 
-7.6 
—20. 7 
-15*9 
+ 9-4 
+47.0 
+89.2 
Do.°. 
Inactive 
-12.3 
-25. I 
-44.6 
+27.8 
+49-9 
New York. 
-11. 7 
-r S .8 
+42-5 
+ 60. I 
+34-9 
+52. s 
Imported. 
Inactive 
Inactive 
+60.0 
+36.6 
+63.0 
+3S-9 
Do.®. 
Inactive 
- 4*9 
“II. I 
“14. 2 
+ 11. 6 
+67. S 
Fraction 
7, 275‘C. 
Minutes . 
+H4- 5 
+177- 7 
a In cold storage i year before distillation. 
