§ 177. ESTIMATION OF THEOBIiOMINE. 187 



§ 177." Tlieohromine. — Trojanowsky found that the theobromine 

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

 -5 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 Aveight of calcined 

 magnesia, and dried in the Avater-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 whilst 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 throAvn on to a tared filter, and Avashed with cold spirit 

 iiill 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, 1876) ; MarkownikoflF, ibid, 

 -xvi. 127, 1877 (Year-book 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 necessary to ensure the success of the estimation. This may 

 •be best accomplished after the beans have been thoroughly dried at 100°C. ; 

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

 sample of coffee 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. Levesie 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 Weyrich, showed the possibility of 

 detecting adulterations, but not of judging of the quality. 



^ ' Beitr. zur pharmacog. und chem. Kenntniss des Cacaos, ' 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 absolute alcohol, and 4284 parts at 17°, and in 105 parts of boiling 

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

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

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

 [3], xiii. 1, 1878 (Year-book of Pharm. 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 prepared 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. For the 

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

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



