160 THE PLANT BASES [CH. 



Expt. 153. Extraction and reactions of nicotine. Weigh out 100 gms. of plug 

 tobacco and boil up the compressed leaves with water in an evaporating dish or in a 

 saucepan. Filter off the extract and concentrate on a water-bath. The concentrated 

 solution is made alkaline with lime and distilled from a round-bottomed flask fitted 

 with a condenser, the flask being heated on a sand-bath. The distillate has an un- 

 pleasant smell and contains nicotine in solution. Test the solution with the alkaloidal 

 reagents employed in Expt. 151. A precipitate will be obtained in each case. 



The nicotine can be obtained from solution in the following way. Acidify the 

 aqueous distillate with oxalic acid and concentrate on a water-bath. Make the con- 

 centrated solution alkaline with caustic soda, pour into a separating funnel and shake 

 up with ether. Separate the ethereal extract and distil off the ether. The nicotine 

 is left behind as an oily liquid which oxidizes in air and turns brown. The alkaloidal 

 tests should be made again with the extracted nicotine. 



Piperine occurs in various species of Pepper (Piper nigrum). The 

 fruit, which is gathered before it is ripe and dried, yields a black 

 pepper, but if the cuticle is first removed by maceration, a white pepper. 

 Piperine is a white solid which is almost insoluble in water but soluble 

 in ether and alcohol. 



Expt. 154. Extraction and reactions of piperine. Weigh out 100 gms. of black 

 pepper. Put it into an evaporating dish, cover well with lime-water and heat with 

 constant stirring for 15-20 minutes. Then evaporate the mixture completely to 

 dryness on a water-bath. Grind up the residue in a mortar, put it into a thimble 

 and extract with ether in a Soxhlet. Distil off the ether and take up the residue in 

 hot alcohol from which the piperine will crystallize out. With an alcoholic solution 

 make the following tests : 



(a) Add the alkaloidal reagents mentioned in Expt. 151 and note that a pre- 

 cipitate is formed in each case. 



(6) Pour a little of the solution into water and note that the piperine is pre- 

 cipitated as a white precipitate. 



(c) To a little solid piperine in a white dish add some concentrated sulphuric 

 acid. It dissolves to form a deep red solution. 



Trigonelline occurs in the seeds of the Fenugreek (Trigonella 

 Foenum-graecum), Pea (Pisum sativum\ Bean (Phaseolus vulgaris), 

 Strophanthus hispidus, Hemp (Cannabis sativa) and Oat (Avena sativa). 

 It is also found in the Coffee Bean (Coffea arabica) ; in tubers of 

 Stachys tuberifera, Potato and Dahlia and in roots of Scorzonera hispanica. 

 It is really a betaine (see p. 157). 



2. The pyrrolidine alkaloids. 



These are derivatives of pyrrolidine, of which the mother substance 

 is pyrrole. (Pyrrolidine is a liquid boiling at 91 C. It is a strong base 

 and forms stable salts with acids.) 



