188 ALKALOIDS. 



the alkaloid from the precipitate. Teu grams of the substance 

 are rubbed down with water to a fine paste, then exhausted by 

 boiling with the same menstruum, filtered and washed with 

 boiling water (700 to 800 cc), as long as alkaloid can be detected 

 in the washings. The mixed aqueous solutions are precipitated 

 with ammoniacal acetate of lead and filtered. The filtrate is made 

 alkaline with caustic soda, evaporated to 50 cc, acidified with 

 sulphuric acid, and again filtered. From the acid solution, which 

 should contain about 6 per cent, of free sulphuric acid, the theo- 

 bromine may be precipitated by warming with phosphomolybdic 

 acid. The precipitate is collected when cool, washed with watei* 

 acidified with sulphuric acid, and dec6mposed by wanning with 

 caustic baryta ; the excess 6f the latter is removed by sulphuric acid 

 and the sulphuric acid by carbonate of barium. The mixture is 

 then filtered whilst hot, evaporated to dryness, and weighed. By 

 deducting the ash the amount of pure theobromine is found. 



§ 178. Estimaium of Piperine. — The. following is Cazeneuve 

 and Caillot's method:^ 10 grams of finely -groulid pepper are 

 mixed with 20 of slaked lime, and enough water to form a thin 

 paste, boiled for fifteen minutes, and then evaporated to dryness 

 on a water-bath ; the residue is finely powdered and exhausted with 

 ether. The piperine obtained by evaporating the ethereal solution 

 is recrystallized from alcohol and weighed. It would, I think, be 

 better if the powdered pepper were first freed from fat by treat- 

 ment with petroleum spirit. Possibly the alkaloid might then be 

 purified by washing with petroleum spirit and water instead of 

 recrystaUizing from alcohol. (Compare also § 64.) 



§ 179. Acidimetric Sstimaiwn of Nicotine. — Schloessing's process, 

 nientioned in § 68, consists in extracting the nicotine by passing 

 the vapour of ether and ammonia through the tobacco, condensing 

 the distillate, alloimblg the ether and ammonia . to evaporate, and 

 titrating the residual nicotine with dilute sulphurip acid. But 

 the alkaloid retains ammonia, and the amount found is conse- 

 quently too high. (Compare Kosutany and my ' Werthbestim- 

 mung.') 



Wittstein, Brandl^ iind Lieclce, all extract the tobacco with, 

 Water acidified with sulphuric acid. Liecke evaporates to a 

 syrup, precipitates with 2 volumes of alcohol, wadies, and again 

 evaporates. The residue is made alkaline with excess of potash, 



' Zaitschr. f. anal. Chem. xvii. 379, 1878 (Year-book of rharm. 42, 1878). 



