May a$, 1914 
Aroma of Hops 
145 
the curves in figures io, n, 12, and 13. These curves show the ester 
numbers of the original oils and the fractions obtained from each oil, the 
general direction being the same in each season. Figures 11, 12, and 13 
show the great similarity from year to year of the ester numbers and 
fractions of the oils from the same section. (See also fig. 1.) It will be 
SO 
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Fig. 12,—Ester-number curves of hop oils from the crops of 1908. 
observed that a very close relationship exists between the oils and the 
fractions from any particular locality. The amount of esters increases 
as the fractionation proceeds until fraction 4 is reached, after which the 
quantity decreases until there is practically none in fraction 7. Appar¬ 
ently the oil highest in esters distills between the temperatures of 185° and 
