78 



found to keep particularly well at low temperatures ; for which reason 

 the cold storage of hops is also to be highly recommended. Lupulinic 

 acid, when boiled with water, yields a bitter solution only when air 

 is bubbled through the liquid during the boiling ; evidently because, 

 by slight oxidation, a water soluble bitter resin is formed. The acid 

 does not, however, suffer any chemical change, but is polymerised in 

 the resinification process. The resinous products obtained by 

 VLAANDEREN are, doubtless, identical with the author's /?-resin. 

 Whether the " hard " and " soft " resins described by BRIANT and 

 MEACHAM 1 , belong to this class of resins, could not be decided ; since 

 it is questionable whether the products named are chemical entities, 

 or mixtures of various resins with CHAPMAN'S hop oil. On oxidation 

 lupulinic acid yielded valerianic acid ; but by reduction no definite 

 product could be obtained. As regards the salts of lupulinic acid, it 

 was found impossible to prepare a copper salt of constant composition ; 

 although preparations were obtained agreeing very well in copper 

 percentages with the copper resin compounds first described by 

 VLAANDEREN another proof that his resin was the fi variety. The 

 experiments relating to the benzoylation of the acid, its behaviour 

 towards acids and silver nitrate solution, and the action of alkaline 

 iodine solution, being of purely chemical interest, may here be omitted. 

 The action of sulphurous acid on lupulinic acid might be of greater 

 interest, as having, possibly a bearing on the " sulphuring " of hops. 

 It was found that sulphurous acid in all its forms is fixed by lupulinic 

 acid. The combination is, however, of so unstable a nature that it 

 is decomposed by water, recrystallisation from methyl alcohol, &c., 

 and for this reason the study of the compound would present great 

 difficulties. It was hoped to obtain some idea of the constitution of 

 the bitter acid by acting on the substance with bromine and iodine ; 

 the main result being to show the existence of double carbon linkings 

 and of one methoxyl group. On prolonged boiling of lupulinic acid 

 with potash-lye, the solution, when acidified, yielded fatty acids 

 closely related to valerianic acid. The most useful indication of the 

 nature of the hop-bitter acid was furnished on fusing it with potash, 

 the results showing that lupulinic acid must be closely related to hop 



1 Transactions of the Institute of Brewing, 1893, 149; 1894, 117. Journal of the 

 Federated Institutes of Brewing, 1896, 408. 



