§ 177. ESTIMATION OF THEOBROMINE. 187 



§ 177. Theobrmnine. — Trojanowsky found that the theobromine 

 in cacao-seeds might be, estimated by the following process * : 

 6 grams of the powdered seed are freed from fat by treatment 

 with petroleum spirit, dried, rubbed down with powdered glass 

 and water to a thin paste, mixed with an equal weight of calcined 

 magnesia, and dried in the water-bath at 60' to 70° C. The residue 

 is again finely powdered, and exhausted by boiling with 80 per 

 cent, spirit. The decoctions are filtered whiJst hot, and evaporated 

 to dryness in a beaker. From the dry extract petroleum spirit 

 will dissolve a little more fat ; after having been again dried, the 

 mass is thrown on to a tared filter, and .washed with cold spirit 

 till nearly colourless. It is then dried and weighed, and to the 

 weight of theobromine thus obtained 0-0007 gram added for 

 every cc. of wash-spirit* 



Wolfram estimates theobromine in- cacao-seeds by precipitating 

 with phosphotungstic acid^ (§ 64), and subsequently separating 



Chem. XV. 474, 1876 (Year-book of Pharm. 20, i876); Markownikoff, ibid. 

 xvf, 127, 1877 (Yearbook of Pharm. 104, 1877) ; Cazeneuve and Caillol, 

 ibid. xvii. 221 , 1878. The latter replace the magnesia in the above method 

 with lime, and the ether with chloroform ; Markownikoff also uses chloroform. 

 In working upon coffee-beans it will be found very difficult to reduce them to 

 the fine powder neces£ary to ensure the success of the estimation. This m».y 

 be best accomplished after the beans have been thoroughly dried a± lOO'C. ; 

 Weyrich, however, has shown that the amount of caffeine contained In a 

 sample of cofTee is no criterion of its quality, and even the estimation of the 

 ash, potash and phosphoric acid in addition to that of the caffeine does not 

 furnish data free from objection. Le vesie estimated (Archiv d. Pharm. [3] viii. 

 298, 1876 ; Journ. Chem. Soc. xxxi. 752) fat, mucilage, tannin and cellulose, 

 but with unsatisfactory results. The determinations of the theine, substances 

 soluble in water, ash, etc., in tea, made by Weyricb, showed the possibility of 

 detecting adulterations, but not of judging of the quality. 



' 'Beitr. znr pharmscog. und chem. KenntnisS des Gacaos,' Diss. Dorpat, 

 1875. This work also contains estimations of the other more important con- 

 stituents of cacao (fat, ash, starch, etc. ) in various samples. 



^ According to determinations made at my request by Treumann, theobromine 

 dissolves in 148*5 parts of water at 100°, and in 1,600 at 17° ; in 422'5 parts of 

 boiling absolnte alcohol, and 4284 parts at 17°, and in 105 parts of boiling 

 chloroform. It differs in its solubility from oafifeine, with which, however, it 

 shares the reaction with chlorine and ammonia. Shaking with benzene does 

 not remove theobromine from aqueoos solutions (§ 55). See Archiv d. Pharm. 

 [3], xiiJ. 1, 1878 (Year-book of Phann. 71, 1879). Basic acetate of lead does 

 not precipitate theobromine from aqueous solution. 



3 Zeitschr. f. anal, Chem.- xviii. 346, 1879 (Year-book of Pharm. 48, 1879). 

 He prepaired his reagent by dissolving 100 grams of tungstate and 60 to 80 

 of phosphate of soda in 500 cc. of water acidulated with nitric acid, i'or the 

 use of phosphotungstic acid as an alkaloid-reagent, see also Scheibler, Joum 

 f. pract. Chem. Ixxx. 211, 1866. 



