436 SCIENTIFIC AND APPLIED PHARMACOGNOSY 



many of the larger grains show lamellae and a circular point of origin 

 of growth or a central fissure, the larger grains show a distinct cross 

 when examined with the micro-polariscope. The powder also 

 exhibits numerous parenchyma cells about 0.065 mm. in diameter, 

 the walls being frequently reddish-brown in color. (Newcomb.) 



Constituents. Starch 35 to 40 per cent, the grains resembling 

 those of potato starch but uniformly smaller; caffeine 1.5 to 3.6 

 per cent; theobromine 0.02 to 0.09 per cent; 1.5 to 4 per cent of a 

 tannin; an enzyme similar to the lipase found in nutmeg and black 

 pepper which decomposes fats. 



Caffeine or theine (trimethyl xanthine or methyl theobromine) 

 also occurs in coffee, tea, cacao, guarana and Mate. It separates in 

 the fovm of acicular crystals having a bitter taste, is soluble in water 

 and alcohol, the solutions being neutral; and may be sublimed with- 

 out decomposition on heating. On treating a small quantity of 

 caffeine with a few drops of nitric acid or chlorin water and evap- 

 orating the solution to dryness on a water bath, the reddish-yellow 

 residue is colored purplish by ammonia. A similar reaction is also 

 obtained by treating the alkaloid with hydrochloric acid and a crystal 

 of potassium chlorate, evaporating the solution and adding a drop of 

 ammonia water to the residue. 



While caffeine can be produced synthetically, it is usually pre- 

 pared from tea and tea dust or sweepings. If crystallized from 

 aqueous solutions it contains one molecule of water of crystallization 

 which is wanting if it is crystallized from alcohol, chloroform or ether. 

 The crystals from aqueous solutions may attain a length of 20 mm. 



At 25 C. one part of caffeine is soluble in 45.6 parts of water; 

 53.2 parts of alcohol; 375 parts of ether; and 8 parts of chloroform. 



Solutions of caffeine give with gold chloride and some other 

 reagents crystalline precipitates. 1 To prepare caffeine gold chloride 

 the caffeine may be dissolved in distilled water, dilute alcohol, abso- 

 lute alcohol or a mixture of equal parts of absolute alcohol and 

 chloroform. One or two drops of the caffeine solution are placed 

 upon a slide, to which is then added one or two drops of an aqueous 

 solution of gold chloride. The two solutions are mixed by the use of 

 a glass rod and then allowed to crystallize. Crystals of caffeine gold 

 chloride are usually formed rather quickly, larger crystals being 

 obtained from the more dilute solutions of caffeine. The crystal are 

 also formed in solutions of caffeine acidulated with hydrochloric acid. 

 The microscopic crystals of caffeine gold chloride vary in length from 



1 Nicholson, Ann. Chem. Pharm., 1847 (62), p. 71; and E. Schmidt, Ibid., 

 1883 (217), p. 283.. 



