75 



advance in the study of the components of hops. He obtained, by ex- 

 traction of lupulin with light petroleum, a highly crystalline substance, 

 very soluble in most organic solvents, but absolutely insoluble in 

 water. Its alcoholic solution tasted intensely bitter. It melted at 

 92-93 C., and he assigned to it the formula CggHggO^. (This 

 ought to be doubled, because of the uneven number of H atoms.) 

 According to BUNGENER, the substance has the character of an 

 aldehyde and of a weak acid ; and he regards as not improbable the 

 view that it is a condensation product of five groups of the amyl 

 series, because, on oxidation, the substance yields valerianic acid. 

 This last point was, however, not proved experimentally. 



GRESHOFF 1 repeated BUNGENER'S work, but was unable to 

 obtain a crystallisable body from lupulin by extraction with petro- 

 leum-ether. Working on the assumption that hop bitter is an alkaloidal 

 substance, he applied various methods (Stas-Otto, Dragendorff, &c.) 

 utilised in the isolation of alkaloids, but did not succeed in obtaining 

 a crystalline bitter substance. 



HAYDUCK 2 extracted hops with ether, and isolated three readily 

 distinguishable resins, two of them bitter, the third tasteless. The 

 former he designated a- and /?-, the latter as y-resin. Under suitable 

 conditions microscopic crystals separate from the a- and /3-resins, 

 being evidently related to them in the sense, as HAYDUCK supposes, 

 that the resins are derived from the crystalline substances, the latter 

 being the oft-found bitter substances of acid character. The tasteless 

 y-resin is possibly derived from the hop oil. The crystalline bodies 

 from HAYDUCK'S resins are described as a- and /3-hop-bitter acids 

 respectively. N 



LINTNER and A. BUNGENER S subsequently prepared the a-resin 

 by HAYDUCK'S method, and isolated therefrom, by repeated 

 precipitation and decomposition of the lead compound, the crystal- 

 lisable a-acid. In alcholic solution it was found to possess a strong, 

 bitter flavour and acid reaction. The acid differs in composition and 



1 Inaug. Dissert, Jena, 1887, 36. 



2 Wochenschrift fur Brauerei 1888, 937 et seq. 



3 Zeitschrift f. d. ges. Brauwesen, 1891, 357. 



