PIPERINE. 449 



Loses its water of crystallization completely at 100 ; 

 fuses at 234-235, and sublimes undecomposed. Weak 

 base. 



If a trace of caffeine is dissolved in chlorine-water 

 and the colorless liquid evaporated, there remains be 

 hind a brownish-red spot, which dissolves in ammonia, 

 forming a beautiful violet solution. 



By t!he action of chlorine or nitric acid on caffeine 

 suspended in water, it is converted into amalic acid, 

 C 12 H 12 N 4 7 (tetramethylalloxahtine, C 8 (CII 3 ) 4 N 4 7 , see 

 Uric acid, p. 237), methylamine and cyanogen chloride 

 being formed at the same time. It forms colorless, 

 difficultly soluble crystals, which become purple in 

 contact with alkalies, and color the skin red. Further 

 action of chlorine causes the formation of cholestrophan, 

 C 5 H 6 SP0 3 ( = dimethyl-parabaiiic acid, C 3 (CH 3 ) 2 N 2 3 , p. 

 235). 



Boiled with alcoholic potassa or with barium hy 

 droxide, caffeine assimilates water and gives^ up car 

 bonic acid, and is converted into an uncrystalline base, 

 cajfeidine, C 7 II 12 N 4 0, easily soluble in water and alco 

 hol. This is a stronger base than caffeine. Its sul 

 phate crystallizes in colorless long needles. When 

 boiled continuously with barium hydroxide, there are 

 formed ammonia, methylamine, carbonic acid, formic 

 acid, and sarcosine (p. 85). 



11. Piper inc. 



Occurrence. In the various kinds of pepper. 



Preparation. Powdered white pepper is exhausted 

 with alcohol ; the solution distilled off until it forms 

 an extract ; this is then washed with water, mixed with 

 potassa, and again dissolved in alcohol. On evapo 

 rating, piperine separates, which is purified by repeat 

 edly dissolving in alcohol, and crystallizing. 



Properties. Colorless, four-sided prisms, without 

 taste or odor, fusing at 100, not volatile. Scarcely 

 soluble in water, easily soluble in alcohol. The solu 

 tion tastes sharp, like pepper, and is neutral. Soluble 



58* 



