ABSTRACTS 



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AGRICULTURAL CHEMISTRY.— Aroma of hops: A study of the 

 volatile oil with relation to the geographical sources of the hops. Frank 

 Rabak. Journal of Agricultural Research 2: 115-159. May 25, 

 1914. 



The paper discusses the aroma of hops grown in various parts of the 

 United States and in Bohemia, the basis of comparison being the volatile 

 oil. Factors which influence the aroma of hops, such as climatic con- 

 ditions and soil, are discussed. Special attention is given to the esters 

 which are the principal odor bearers of the oil. In order that a logical 

 comparison of the various hops may be made, the volatile oils distilled 

 from the several hops are carefully compared as regards their physical 

 and chemical properties. This scheme of comparison is carried through 

 four successive seasons to ascertain whether any constant similarities 

 or differences exist in the oils, especially in the oils distilled from foreign 

 and domestic hops. 



Comparisons are made of the yields of volatile oil from the various 

 hops; the physical properties, including color, odor, taste, specific 

 gravity, refraction, and solubility; and the acid, ester, and saponification 

 numbers of the oils. The oils are subsequently fractionated and the 

 properties of the fractions compared. Tables and curves showing the 

 differences in the oils are included. 



A detailed chemical examination of a sample of the volatile oil of hops 

 is given and the approximate composition indicated. Important differ- 

 ences in the oils are apparent, not only durmg any particular season but 

 for several seasons. The curves show these constant differences in 

 properties most forcibly. The curves of ester content show remarkable 

 differences in the oils from the several geographical sources, the imported 



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