65 



activity is probably due to the presence of a trace of some active 

 substance. 



The Third Fraction. This consisted of a derivative of the above 

 alcohol, namely, linalyl isononoate, and was a colourless liquid 

 with a marked though less fragrant odour than that of the linalool 

 itself. 



The Fraction of Highest Boiling Point. This fraction consisted of 

 a nearly colourless liquid of much less mobility than any of the pre- 

 ceding, and boiling at 263-266C. under atmospheric pressure. Its 

 sp. gr. =0-9001 at 15 15 and its analysis and vapour density deter- 

 minations showed it to have the formula C 15 H 24 . This sesquiter- 

 pene, for which I suggested the name humulene, is a well characterised 

 substance, readily forming a number of crystalline derivatives, which 

 have been described in a paper communicated to the Chemical Society, 

 and published in the Transactions of that body. It occurred to the 

 extent of about 40 per cent, in the majority of the samples of oil 

 which I examined. 



Humulene, when pure, has very little odour, and does not 

 undergo much change when exposed to the air. It has, therefore, 

 but little effect On those properties of the oil which are of chief 

 technological importance, and may be regarded rather in the light 

 of a diluent. The oil of hops, therefore, contains the following 

 compounds : Myrcene, humulene, linalool, linalyl-isononoate, 

 probably traces of some ester of geraniol, and a small amount of a 

 diterpene. In all the freshly distilled samples of oil with which I 

 worked the hydrocarbons myrcene and humulene were present to 

 the extent of 80 to 90 per cent. 



It is well known that marked differences exist between the 

 aroma of hops grown in different parts of the world, and that these 

 are resident in the essential oils. No one, for example, relying on 

 the sense of smell alone could mistake Californian for Bavarian 

 hops, or the latter for the produce of Kent. It is interesting in this 

 connection to note that these variations, readily recognised as they 

 are by the nose, yet correspond with such slight differences in 

 chemical composition that the methods available for the separation 



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