76 



solubility from the bitter substance obtained by H. BUNGENER, the 

 difference being particularly marked in the form of the crystals. 

 The a-acid crystallises in small rhomboids, whereas the /3-acid (H. 

 BUNGENER'S) forms long, massive prisms, or fine, felted needles. 



SEYFFERT 1 who also investigated the hop resins later on, slightly 

 modified HAYDUCK'S method, and gave some details concerning the 

 ether-copper reaction of the a-acid, which he was able to obtain quite 

 pure by means of ice-cold petroleum. He proposes the same solvent 

 for the /2-acid (crystals from the /?-resin). 



In addition, SEYFFERT refers to a crystalline body, which he 

 obtained from the y-resin, but gives no details as to its properties. 



In continuation of these researches, and in collaboration with 

 V. ANTROPOFF 3 , he proposed an improved method for the preparation 

 of the /3-hop-bitter acid, particular stress being laid on the exclusion 

 of air (working in a current of carbon dioxide) and the avoidance of 

 high temperatures. 



The different preparations obtained by the above, as also by 

 BUNGENER'S method, all exhibited very ill-defined melting points, 

 varying distinctly from that (92-93 C.) founded by BUNGENER. 

 Apart from this, the variations in the carbon and hydrogen per- 

 centages, indicated that impure substances were being dealt with, 

 According to these investigators LERMER'S bitter-acid is not identical 

 with the a-acid, but the body described by them as the a-acid, 

 although possessing faintly acid properties, to all appearances 

 belongs to a very different class of substances. According to 

 them the hop resins are a mixture of bodies undergoing continuous 

 and increasing decomposition. 



If we stop now to consider the results of the preceding investiga- 

 tions, several inconsistencies become apparent. The chemical nature 

 of the bitter substances remains quite undecided, and not even the 

 elementary composition and molecular weights of the bitter acids are 

 known with any degree of precision. Only so much is certain, that 



1 Zeitschrifi f. d. ges. Brauwesen, 1892, Nos. 4, 5 and 6. 



2 Zeitschrift /. d. ges. Brauwesen, 1896, Nos. i and 2, 



