STROBILI HUMULI. 553 



colour and become brown, at the same time acquiring an unpleasant 

 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 brewei*s 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 (187G, 1878) hinnulotannic acid and jMoha- 

 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 oft' water, 

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



humulotannic acid. phlobaphene. 



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

 loses water and furnishes glucose. 



From raw phlobaphene ether removes the bitter principles of hops, 

 a colourless crj-stallizable and a brown amorphous resin, besides chloro- 

 phyll and essential oil. 



By distilling hops with water, 0*9 per cent of essential oil are 

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

 passes into valerianic acid ; the latter in fact occurs in the glands, yet 

 according to Mehu" only to the extent of 01 to 017 per cent. When 

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

 reddish-brown when old hops have been employed. We find it to be 

 devoid of rotatory power, neutral to litmus paper, and not striking any 

 remarkable coloration with concentrated sulphuric acid. 



Griessmayer (1874) has shown that hops contain Trimethylamine, 

 and in small proportion a liquid volatile alkaloid not yet analysed, 

 which he terms Lupidine. The latter is stated to have the odour ot 

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

 jotassium and sulphuric acid. 



Lastly, Etti also found arable (pectic) acid, phosphates, nitrates, 

 lalates, citrates, and also sulphates, chiefly of potassium, to occur in 

 'hops. The amount of ash afibrded by hops dried at 100° C. would 

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



Production and Commerce — England was estimated as having in 

 1873, 63,276 acres under hops. The chief district for the cultivation is 

 the Qounty of Kent, where in that year 39,040 acres were devoted to this 

 plant. Hops are grown to a much smaller extent in Sussex, and in still 

 diminished quantity in Herefordshire, Hampshire, Worcestei-shire and 

 Surrey. The other counties of England and tJie principality of Wales 

 produce but a trifling amount, and Scotland none at all. 



In continental Europe, hops are most largely produced in Bavaria and 

 Wurtemberg, Belgium and France, but in each on a smaller scale than in 

 England. France in 1872 is stated to have 9223 acres under hopa' 



^ A substance with which we are not ' Agricultural Returns of Great Britain, 



acquainted. &c., 1873, presented to Parliament, 48. 49. 



" TU«e, Montpellier, 1867. 70. 71. 



