77 



there are two crystallisable bitter substances of slightly acid 

 character ; further that hops contain at least three resins, of which 

 two are bitter and one is tasteless. It is highly probable that the 

 bitter resins are closely related to the crystallisable bitter acids, 

 which, therefore, for the present, may be distinguished as the a- and 

 y8-acids. H. BUNGENER'S acid is the (3 compound, and, in view of 

 the thorough nature of his researches, the empirical formula assigned 

 by him to the acid is in all probability correct. The a- and /2-acids 

 are undoubtedly dissimilar in composition. 



This conclusion may be deduced from the work of LINTNER and 

 A. BUNGENER, also from that of H, BUNGENER, SEYFFERT, and 

 ANTROPOFF. 



Further, it appears fairly certain that LERMER'S acid must be 

 identical with the /3-acid described by H. BUNGENER and SEYFFERT. 



LiNTNER, 1 together with the author, instituted further researches 

 on hop-bitter, operating on lupulin, and directed particularly towards 

 the study of the a- and /3-acids. The method for preparing the 

 /2-acid was worked out so far, that it is now possible to obtain larger 

 quantities of this body with relatively little trouble. Methyl alcohol 

 was found to be a most useful solvent, and by its aid crystals up to 

 i cm. in length were obtained. The formula of lupulinic acid was 

 found to be C 25 H 36 O 4 , and BUNGENER'S formula C 50 H 70 O 8 is, 

 therefore, incorrect. Lupulinic acid, on exposure to air, develops an 

 odour resembling that of fatty acids, and is converted into a yellow 

 resin. That oxygen from the air plays a part in this change appears 

 from the following experiments : 



Lupulinic acid was enclosed in small glass tubes, one of which 

 was filled with hydrogen and sealed, the other left open at both ends. 

 The tubes were then exposed to light, near a window, for several 

 months. At the end of this time, the acid in the open tube had 

 become quite yellow and " cheesy," whilst that in the sealed tube 

 remained perfectly white. In another similar experiment, the tubes 

 were preserved in a closed box. The result was the same, showing 

 that light is not an essential factor in the change. The acid was 



1 Zeitschrift f. d. ges. Brauwesen, 1901, 500. 



