288 HOPS. 



Chemical analysis of hops. — The estimation of the total 

 constituents being a troublesome and difficult task, and of 

 no great value in judging quality, the analysis is usually 

 restricted to determining the percentage of moisture, the 

 matter soluble in petroleum spirit, the test for sulphuring, 

 and occasionally the percentage of hop tannin. 



Moisture (Prior) is estimated by drying 4 to 5 grams of 

 dismembered cones on watch - glasses over concentrated 

 sulphuric acid in vacuo and at ordinary temperature until 

 constant weight (two weighings on successive days) is 

 attained. 



Matters soluble in petroleum spirit. — ^About 5 grams of the 

 dried hops (as above) are placed in a Schleicher and Schiill 

 extraction cylinder, previously dried at 100° C. and tared with 

 weighing-glass. After re-weighing to ascertain the exact 

 weight of hops taken, the cylinder is placed in a Soxhlet 

 apparatus, treated with sufficient petroleum spirit to allow 

 of a suitable quantity draining down into the flask, and 

 extracted for 8 to 10 hours under a reflux condenser. 

 Lintner has recently brought out a titrimetric method for 

 estimating the soft resin. 



Tannin. — See page 530 of Dr. J. Konig's work, already 

 referred to, viz., Die Untersuchung landwirthschaftlicht und 

 gewerblich wichtiger Stoffe (Berlin, 1898). 



The test for sulphuring has already been given in the 

 section on storage. 



JUDGING THE VALUE OF HOPS. 



Hops are still principally judged by certain external 

 characteristics, the numerous attempts to found a scientific 

 basis of valuation having been so far unattended with 

 satisfactory results. The estimation of the lupulin is, if 

 not altogether worthless, at any rate without much value. 



