STROBILI HUMULI 553 



colour and become brown, at the same time acquiring an un])]ca.snnt 

 odour, by reason of the formation of a little valerianic acid. Exposure 

 to the vapour of sulphurous acid retards or prevents this alteration. For 

 medicinal use, hops smelling of sulphurous acid should be avoided, 

 though in reality the acid speedily becomes innocuous. Liebig has 

 refuted the objections raised by brewers to the sulphuring of hops. 



Chemical Composition — Besides the constituents of the glands 

 which are described in the next article, hops contain according to Etti's 

 elaborate investigations (1876, 1878) humid of annic acid and iMuha- 

 phene. The former is a whitish amorphous mass, soluble in alcohol, hot 

 water or acetic ether, not in ether. By heating the humulotannic acid at 

 130° C, or by boiling its aqueous or alcoholic solutions, it gives off water, 

 and is transformed into phlobaphene, a dark red amorphous substance, 



humulotannic acid. plilobapheue. 



The latter substance, on boiling it with dilute mineral acids, again 

 loses water and furnishes glucose. 



From raw phlobaphene ether removes the hitter principles of hops, 

 a colourless erystallizable and a brown amorphous resin, besides chloro- 

 phyll and essential oil. 



By distilling hops with water, 0-9 per cent, of essenttal oil are 

 obtained. Personne (1854) stated it to contain Valerol^ C^H^ 0, which 

 passes into valerianic acid; the latter in fact occurs in the g'^nds yet 

 according to Mdhu^ only to the extent of 01 to 017 per cent. U hen 

 distilled from the fresh strobiles the oil has a greenish colour but a 

 reddish-brown when old hops have been employed. A\ e lind it to be 

 devoid of rotatory power, neutral to litmus paper, and not striKmg an} 

 remarkable coloration with concentrated sulphuric acid. 



Griessmayer (1874) has shown that hops contain Tnmethyl amine, 

 and in small proportion a liquid volatile alkaloid not yet analysed 

 which he tevml Luimlme. The latter is stated to have the odour ot 

 Conine, and to assume a violet hue when treated with chromate ot 



potassium and sulphuric acid. , , , , ^th-^Ipq 



I Lastly, Etti also found arable (pectic) acid, phosphates, mtiates, 

 malates, citrates, and also sulphates, chiefly of potassium to occuim 

 hops. The amount of ash afforded by hops dried at lOU U. wouui 

 appear to be on an average about 6-7 per cent. ^ . 



^^ Production and Commerce -England ^^;as f t^^^^jf ^X^^^^ 

 1873, 63,276 acres under hops. The chief district ^^ J^,;"^^^^^^^^ 

 the county of Kent, where in that year 39,040 acres w^erd^^ 



arp crmwn to n, much smaller extent in bussex, ana 



Hop 



Hereford 



A substance withwhicl 

 »^quauited. 



' TMie, Montpellier, 1867. 



I AgrlcdUiral Returns of Great Brkavu 

 &c., 1873, presented to rarhameut, 48. 49. 



70. 71. 



