74 



solution. The latter, when evaporated in vacua over strong sulphuric 

 acid, deposits well-formed, colourless crystals ; but if concentrated 

 on the water bath yields an extract, and very few crystals. 



The crystals, as also the syrup obtained on the water bath, 

 possess a strong, bitter flavour, and are soluble in water, especially on 

 warming to a bright solution. ETTI states that the precipitated resin, 

 if repeatedly redissolved in water and reprecipitated, may be 

 resolved completely into bitter substance and resin, the latter 

 retaining no bitter flavour whatever. 



In addition, ETTI distinguishes between the amorphous brown 

 resin, and the bitter substance proper, regarding them as distinct 

 substances. 



IssLEiB 1 repeated these experiments as to the precipitation of the 

 resin from alcoholic solution by water, but arrived at different results. 

 He was the first to draw attention to the discordant nature of the 

 statements, to be found in the literature of the subject, relating to the 

 properties of hop bitter. He made use of the property of bone char- 

 coal of absorbing certain bitter principles, for preparing hop bitter 

 from aqueous decoctions of hops or of lupulin ; and he describes the 

 bitter substance and some of its reactions. He ascribes to this hop 

 bitter the formula C 29 H 46 O 10 , based on the elementary composition, 

 and particularly on the products of hydrolysis by dilute sulphuric 

 acid lupulieretin C 10 H 16 O 4 and lupulinic acid C 48 H 82 O 19 . 



ISSLEIB also gives the analysis of a barium salt of lupulinic 

 acid, and of some other resinous compounds. 



OTT/ in general, confirms LERMER'S findings concerning his 

 hop-bitter acid, but detects some difference in the reactions of the 

 ether soluble copper salt, which he finds readily decomposable by 

 hydrogen sulphide, whilst LERMER affirms it to be stable. 



BuNGENER's 8 researches on hop-bitter acid marked a distinct 



1 Archiv der Pharmacie, 1880, 216, 345-363. 



2 Zeitschrift f. d. ges. Brauwesen, 1880, 201. 



3 Bulletin de la Societe Chimique de Paris, 1886, 45, 487-496 ; also Zeitschrift 

 . d. ges. Brauwesen, 1884, 93. 



