14: HISTORY, BOTANY, ECONOMIC USES, 



Besides the oil which is obtained by distillation, and the 

 tannic acid, which is also not without value as regards 

 the preparation of beer, the resin and the bitter substance 

 especially deserve to be distinguished. They are both ob- 

 tained by treating with alcohol the yellow dust of the hops. 

 Water is added to this tincture, and it is distilled, which 

 causes the separation of a large quantity of resin. The 

 tannic acid and malic acid are saturated by means of lime, 

 and the liquor is evaporated. If the residue is treated by 

 ether to further obtain a small remaining quantity of resin, 

 then by alcohol, the bitter substance dissolves in the alcohol, 

 and may be separated from it by evaporation. 



Lupiiline, seen under the miscroscope, resembles an acorn 

 in its cupule; it is a gland composed of a hidden cupule, 

 surrounded by a membraneous sac, called the euticule, which 

 contains the products of the secretion, constituting the 

 essential oil of hops. 



This essential oil is a clear green liquid, slightly bitter, 

 very aromatic, of the mellow odour of fresh hops ; its specific 

 weight = 908 at + 16 C. ; it is but slightly soluble in water, 

 very soluble in alcohol, and boils at -j- 240 C. Iodine and 

 bromine turn it brown and alcoholized sulphuric acid reddens 

 it. The essential oil is composed of an eleoptine and a stear- 

 optine. The eleoptine is a hydrocarbon, C 10 H 8 , isometric 

 with spirits of turpentine, and distils at + 175 C. The 

 stearoptine is an oxygenized hydrocarbon C 10 H 12 2 , isomeric 

 with valerol, which distils at -}- 210 C., and is converted by 

 oxidation into valerianic acid. 



The chemical composition of lupuline proves the richness 

 of its principles, for analysis has found in it the following : 



