378 FOOD AND FOOD ADULTERANTS 



tered and further concentrated to about 150cc. I prefer sulphuretted hydrogen to 

 sulphuric acid or a sulphate, as the lead sulphide seems to carry down a notable 

 quantity of coloring matter. 



The treatment with lead acetate removes all tannin, phosphates, &c., and the hop- 

 resin and lupulin are also completely precipitated, while all or nearly all hop substitute* re- 

 main in solution. 



The next object is to separate the sugar, dextrin, and mineral constituents of the 

 beer as perfectly as possible from the active principles of the various hop substitutes. 

 Instead of precipitating the carbo-hydrates, &c., by excess of strong alcohol, I pre- 

 fer to remove the bitters from the aqueous liquid itself by agitation with suitable im- 

 miscible solvents. 



The object being to extract as many active principles as possible in the simplest 

 possible way, leaving their mutual separation and recognition for further considera- 

 tion, I employ chloroform as having the most general solvent action. It separates 

 with tolerable ease from the aqueous liquid, and should be employed as long as it 

 leaves a notably bitter residue on evaporation. In many of my experiments I rclitd 

 on the traces of lactic and other acids naturally present in beer to produce the requi- 

 site degree Of acidity, but I am now of opinion that the addition of a little "dilute 

 sulphuric acid is advantageous, if not actually necessary, in some cases. The extrac- 

 tion with chloroform being complete, ether should next be used, the treatment be- 

 ing repeated as long as any notably bitter principle is extracted. Finally, the aque- 

 ous liquid is rendered alkaline with ammonia, and agitated with chloroform or ether- 

 chloroform, to extract any alkaloids. 



The following arrangement shows the behavior of the more important bitter prin- 

 ciples when the aqueous liquid is agitated in succession with chloroform, ether, and 

 ammonia, and ether-chloroform. I have personally verified the behavior of the sub- 

 stances to the names of which asterisks are attached. 



(1) Extracted by chloroform from acid solutions: 



Absiiithiu (wormwood). 

 "Anthemin (chamomiles). 

 Colchicine (colchicum), imperfectly. 



* Colocynthin (colocynth, or bitter apple), imperfectly. 



* Calumbin, and probably some berberine (calumba), bright yellow and highly 

 fluorescent. 



* Gentipicrin (gentian), very imperfectly. 



* Picric acid (artificial), yellow, imperfectly. 

 Picrotoxin (cocculus indicus"), with difficulty. 



* Quassiin (quassia wood). 



(2) Subsequently extracted by ether from acid solutions : 



*Chiratin (chiretta). 



* Colocynthin (colocynth, or bitter apple). 



* Gentipicriu (gentian). 

 Picric acid, yellow. 

 Picrotoxiu (coccnlus indicus). 



(3) Subsequently extracted by ether-chloroform from alkaline solutions: 



* Berberine (calumba root). 

 Colchicine (colchicum.) 



By evaporating off the solvent, warming the residue with a little alcohol, and then 

 adding water, solutions are obtained which will be bitter if any of the above sub- 

 stances be present. A very small quantity of the substance is required for this te^! : 

 indeed, the use of too large an amount must be carefully avoided or the sense of taste 

 will be found to be wholly paraly/.ed for the remainder of the day at any rate. 



It will be seen that chloroform or ether extracts from acidulated aqueous liquids 

 almost the whole of the above bitters. The subsequent treatment with ether- 

 chloroform in alkaline solution is usually unnecessary, as t he principles of calumba and 



