APPENDIX A. 379 



colchicnm are in part extracted by acid chloroform. Seeing that the bitter princi- 

 ples of hops are entirely precipitated by neutral acetate of lead, the presence of some 

 hop substitute is absolutely certain if the chloroform or ether residue has a marked Mtter 

 taste. This can be ascertained in the course of a few hours by the simple method 

 above indicated, and half a pint of the beer is amply sufficient for the purpose. 



The presence of a hop substitute being proved by the marked bitter taste of the 

 chloroform or ether extract it -will of course be very desirable to ascertain its nature, 

 and in some important cases this can fortunately be effected very satisfactorily. In 

 others we may expect future investigation to afford the necessary assistance. 



I have made special endeavors to ascertain the possibility of definitely recognizing 

 quassia, which is one of the most important of the hop substitutes actually employed. 



For this purpose I prepared quassiin in a moderately pure state by exhausting 

 quassia wood with hot water and treating the decoction with acetate of lead and 

 chloroform, in the manner recommended for beer. The. quassiin was obtained with 

 some difficulty in a distinctly crystalline state and otherwise it presented a close gen- 

 eral resemblance to the description of it given by other observers. The following 

 characters and tests were specially verified : 



Quassiiu is intensely and persistently bitter, sparingly soluble in cold water, more 

 reailily in hot, and easily soluble in alcohol. Its best solvent is chloroform, which 

 extracts it readily from acidulated solutions. 



An aqueous solution of quassiin does not reduce Fehliug's solution, or ammonio- 

 nitrate of silver. The solid substance gives no coloration (or merely yellow) when 

 treated with strong sulphuric acid or with nitric acid of 1. 25 specific gravity, nor is 

 any color produced on warming. These four negative reactions are important, for 

 picroloxin reduces Fehling's solution and gives an orange-red color with sulphuric 

 acid ; (jcntipicrin and menyanthin reduce ammonio-nitrate of silver, and the former 

 gives a red color and the latter a yellowish brown, changing to violet red when 

 warmed with sulphuric acid, and other bitters mostly give more or less characteristic 

 reactions. 



A solution of quassiiu gives a white precipitate with tannin. The reaction is used 

 by Christensen, Oliver!, and others to-isoiate quassiin from its solutions, and by En- 

 ders to separate it from picrotoxin. In my hands the reaction has not proved satis- 

 factory. The liquid is very difficult to filter and the filtrate still retains an intensely 

 buter taste, showing that the precipitation is very incomplete. As an analytical 

 method the reaction is useless, but it is of some value as a qualitative test. 1 The test 

 must be made in a cold solution. 



Qnassiin gives a brown coloration with ferric chloride. The reaction is best ob- 

 served by moistening a quassiin residue in porcelain with a few drops of a weak 

 alcoholic solution of ferric chloride, and applying a gentle heat. A fine mahogany- 

 brown coloration is produced. 



The most delicate and characteristic test for quassiin is based on an observation of 

 Christensen. On treating quassiin with bromine a derivative is obtained, which is 

 stated to be more bitter than the original substance. On adding caustic soda the 

 bitter taste is said to be destroyed, but a product of a fine yellow color is obtained. 

 I am unable to confirm the destruction of the bitter taste, at least entirely, but the 

 coloration is marked and characteristic. 



The following is the best way of applying the test : The substance to be tested for 

 quassiin is dissolved in a little chloroform, or if a liquid is agitated with chloroform, 

 and the aqueous layer separated. The chloroformic solution is then treated with 

 bromine water until the yellow color remains after agitation, showing that the bro- 

 mine has been used in slight excess. The aqueous liquid is then removed (or if small 

 in volume may be neglected), and the chioroform agitated with anwaonia. This pro- 

 duces iur.nediato destruction of tho color duo to the bromine, and if quassiiu be ab- 



' Possibly more complete precipitation of quassiin by tannin could be effected in an 

 alcoholic solution. 



