284 . HOPS. 



isolated, one corresponding to the a resin and the other to 

 the ;S resin. Both the a and the /3 lupulinic acid are in the 

 form of small rhombic crystals, insoluble in water, but dis- 

 solving to a bitter solution in alcohol. On long exposure 

 to the air the colourless crystals turn reddish yellow, and 

 are finally converted entirely into resins, giving all the re- 

 actions of the corresponding parent resins. The /8 acid 

 proved to be fully identical with Bungener's acid, and 

 probably Lermer's acid is none other than yS lupulinic acid.^ 



Hop tannin? — Tannic acid is present in the bracts, stalks, 

 strigs, and to a small extent in the lupulin granules, of the 

 hop cone. It forms a light brown amorphous powder, which 

 is only sparingly soluble in water, but dissolves readily in 

 dilute alcohol and acetic ether, and has an astringent taste. 



In solution it gives an intense green coloration in pres- 

 ence of ferric chloride, but no precipitate. By the conversion 

 of tannic acid there is formed a reddish brown substance 

 (phlobaphene) only sparingly soluble in water and alcohol. 



Hanamann^ examined eight samples of Bohemian hops 

 by the Carpere-Barbieri method, and found the tannic acid 

 content to vary between 4'38 per cent, and 6'05 per cent, of 

 the total dry matter, the higher percentage being from the 

 finest hops. 



Etti gives the formula of tannic acid as C25H24O13. Little 

 is known as to the tannic acid of hops ; nevertheless, it was 

 and is credited — in conjunction with the phlobaphene — with 

 the power of precipitating the readily decomposable al- 

 buminoids of beer wort, and thereby acting indirectly as a 

 preservative against the injurious reactions to which these 

 substances could give rise. 



^ Zeitschrift far das gesammte Braicioesen, 1892, 1896. 



^ Dr. E. Prior, Chemie und Physiologie des Mahes und des Bieres, Leipzig, 

 1896. 



^ " Untersuohungen von Hopfen und Hopfenerden," Zeitschrift fUr das 

 landwirthschaftliche Versuchswesen in Oesterreich, Vol. I., No. 6, 1898. 



