STEUCTTJEE OF THE HOP CONE. 283 



boiling their antiseptic properties became impaired : probably 

 their conversion into inert 7 resin may account for this. 



The hitter principle. — Lermer succeeded in isolating from 

 hops, and even from beer, a white crystalline substance,, 

 which he termed lupulinic acid. This body, insoluble in 

 water, disolves in alchohol, and in this solution exhibits an 

 intensely bitter flavour, recalhng the bitter taste in beer.. 

 He ascribed to it the formula of CggHjoO^, and believed that,, 

 notwithstanding its insolubility in water, it is the cause of 

 the agreeable bitter flavour of beer. 



Etti discovered in the ethereal extract of hop cones a 

 similar bitter crystalline body, which, however, differs from 

 Lermer's acid in being soluble in water. 



The bitter principle extracted from hops by Issleib was 

 identical in solubility and bitter flavour with that found by 

 Etti. 



The lupulinic acid prepared by Bungener resembled that 

 of Lermer, being insoluble in water and not developing its. 

 bitter flavour until dissolved in alcohol. He gave it the 

 formula G2^^fi^,^ and mentioned its ready solubility in 

 alcohol, ether, benzol, chloroform, carbon bi-sulphide, and 

 glacial acetic acid; also, that it melts at 92° to 93° C. 

 Originally in doubt, he subsequently recognised it as the 

 cause of the agreeable bitter flavour in beer. 



When exposed to the air pure lupulinic acid gives off 

 an odour of valerianic acid, on which account it is considered 

 that it is the lupulinic acid, and not the ethereal oil, which; 

 undergoes oxidation and' develops the rotten cheesy smell 

 of old hops. 



According to reports from the laboratory of the Kalinkin 

 Brewery, St. Petersburg,^ two lupulinic acids have been 



^More recently Lintner and Barth corrected the formula to 02.5113804^ 

 [Zeitschrift fur das gesammte Brauwesen, 1898, No. 45). 

 ^ Zeitschrift filr das gesammte Bratiivesen, 1892, 1896. 



