382 BEER, BAVARIAN 



Hof&tedt's process for the detection of spurious bitters in beor is applicable to the 

 detection of picrotoxin, absinthin, monyanthin, quassin, and colocyuthin. The bitter 

 principles likely to occur in beer may bo divided into two classes : 



I. PHECIPITABLE BY ACETATE OF LEAD. 



Lupulin. It is not precipitablo by tannin. It is soluble in alcohol and ether, but 

 not in water. 



II. NOT PRECIPITATED BY ACETATE OF LEAD. 



With tannin, after removal of lead by means of sulphuretted hydrogen. 



a, Not precipitated by tannin : 



Picrotoxin. Soluble in water, alcohol, and other. 

 Absinthin. Soluble in alcohol and ether, not in water. 



b. Precipitated by tannin : 



Menyanthin. Sparingly soluble in ether and cold water ; easily in hot water. 



Turns brown and then violet with strong sulphuric acid. 

 Quassin. Sparingly soluble in ether ; soluble in 222 parts of cold water ; 



not coloured by sulphuric acid. 

 Colocynthin. Insoluble in ether ; soluble in cold water. Turns first rod and 



then brown with strong sulphuric acid. 



The quantities needful for examination are six litres of Bavarian or bitter beer, or 

 four of porter. This_ may seem excessive, but it must be remembered that a very 

 small quantity of the above-mentioned drugs will impart a strong bitter taste to a 

 large volume of liquid ; and, again, that the hop is never entirely omitted, since its 

 peculiar efficacy in preventing spurious or secondary fermentation appears to be 

 possessed by no other bitter. The beer in question is to bo evaporated down, first 

 over the naked fire, and afterwards on the water-bath. Great care must be taken 

 that it does not dry or burn on the sides of the vessel, or bitter principles may be 

 generated which mask the reactions to be sought for. The thick mass is well 

 treated with alcohol in a tall beaker. At the bottom will be found a thick gummy 

 mass, and a somewhat turbid stratum of liquor over it : this is set aside to become 

 clear ; it is then poured off and the alcohol distilled off; the residue is concentrated to 

 a syrup and dissolved in alcohol. The solution is mixed with ton times its bulk of 

 ether, which precipitates sugar ; when clear, the liquid is decanted from the sediment 

 and distilled. The residue is dissolved in warm water and a portion of it tested with 

 tannin. A pure, well-hopped beer never gives a clear aqueous solution ; a beer con- 

 taining little of the hop may ; if the solution does not clear up add a trace of alcohol. 

 Besides lupulin, absinthin is insoluble in water. Filter off the resinous matter which 

 may have been deposited, then precipitate the warm filtrate with acetate of lead, which 

 must not be too acid ; lupulin is then thrown down. Excess of lead must be carefully 

 avoided, or menyanthin may fall down also : allow it to settle, filter, and wash the 

 precipitate with hot water. 



Filtrate. Treat with sulphuretted hydrogen till all the lead is precipitated ; 

 filter and wash, first with warm water and then with alcohol ; remove sulphuretted 

 hydrogen and free acetic acid by evaporation almost to dryness. If the residue is 

 free from bitterness no adulteration is present ; absinthin never gives a clear aqueous 

 solution, and menyanthin never a clear cold one. A turbid solution may contain all 

 the spurious bitters ; add a little alcohol till the solution becomes clear, and then 

 tannin. 



1. The precipitate formed is dried up along with hydrated oxide of lead suspended 

 in water, and extracted with boiling spirit. In the residue of this extract colocynthin, 

 menyanthin, and quassin aro separated by means of their behaviour with ether and 

 water. 



2. The precipitate is freed from tannin by means of acetate of lead, the precipitate 

 filtered off, the lead removed by means of sulphuretted hydrogen and evaporated. 

 Picrotoxin separates out in crystals ; absinthin remains as a yellow mass. 



Levin Ender recommends the following procedure : 



1 . Precipitate with acetate of lead. 



Lupulin. It gives no mirror with ammoniacal solution of silver. 



2. Not precipitated by acetate of lead, but by tannin. 



A. Soluble in ether : Absinthin. Gives a mirror with the silver solution. 



B. Sparingly soluble in other. Menyanthin; Quassin. The former gives a 



mirror ; the latter not. 



Picrotoxin, absinthin, menyanthin, edocynthin, reduce solution of silver ; lupulin 

 and quassia do not. 



