DETERMINATION OF THEOBROMINE. 953 



bath with continual stirring. The residue is extracted with CHC1 3 and the chloro- 

 form distilled off. The residue is dissolved in hot water, the solution filtered, evap- 

 orated to dryness, and the residue of theobromine dried and weighed. This method 

 includes the traces of caffeine which are present in cocoa. This may be isolated by 

 extracting the residue of theobromine with cold benzol, which dissolves only the 

 caffeine. The benzol is distilled off, the residue shaken with water, and the solution 

 filtered and evaporated. 



Weigrnann. 1 Twenty grams of the material are rubbed up into a soft paste with hot 

 water; more water is then added and the mixture is boiled for fifteen to thirty min- 

 utes. The decoction is then made up to one liter, allowed to settle, and 500 cc 

 filtered off. This is brought to a boil and precipitated with ferric acetate. The pre- 

 cipitate is filtered off, the filtrate concentrated on the water bath, strongly acidulated 

 with H. 2 SO 4 (the liquid should contain at least 6 per cent H 2 SO 4 ), and precipitated 

 with sodium phosphomolybdate. After standing two to three hours the precipitate 

 is filtered off, washed with acidified water, and its content of nitrogen determined 

 after drying. The results thus obtained are somewhat lower than Wolfram's. 



Wolfram. 2 If the bean deprived of husks is to be examined, it is first rubbed to a 

 paste in a hot mortar. Ten grams of this mass, or 20 to 30 grams of chocolate, are 

 treated for some time with boiling water, ammoniacal lead acetate added, the solution 

 filtered hot, and the precipitate washed lentil a drop of the filrate after cooling gives 

 no precipitate with sodium phosphomolybdate. A volume of 700 to 800 cc is gen- 

 erally necessary. After the addition of NaOH, the filtrate is evaporated to 50 ce. It 

 is then strongly acidulated with H. 2 SO 4 and the lead sulphate separated by filtration. 

 The filtrate is mixed with a large excess of sodium phosphomolybdate (this reagent is 

 prepared by dissolving 100 grams of sodium molybdate and 60 to 80 grams of sodium 

 phosphate in 500 cc of water acidulated with about 6 per cent of nitric acid). Heating 

 and stirring facilitates the settling of the precipitate. After standing several hours 

 the liquid is filtered and the precipitate washed with 6 to 8 per cent H 2 SO 4 . The 

 filter and precipitate are placed in a beaker and Ba(OH) 2 added until the reaction is 

 alkaline. Heating renders the decomposition more rapid. The excess of Ba(OH) 2 is 

 neutralized with H.jSO 4 , and any possible excess of the latter with BaCO 3 . The 

 whole is filtered and washed hot; the filtrate is evaporated in a platinum dish and 

 the theobromine dried and weighed. As barium salts may be present, it is best to 

 ignite, moisten with (NH 4 )iCO 3 , reignite and weigh. The difference is theobromine. 



Zipperer. 3 The substance is extracted with petroleum ether and then three times 

 extracted with 80 per cent alcohol. The alcoholic extracts are evaporated to dry- 

 ness on the water bath with 15 grams of Ca (OH). 2 . The dry residue is extracted with 

 CHCL, the latter distilled off, the residue dissolved in hot water, the solution 

 filtered and evaporated to dryness. The resulting theobromine is dried and weighed. 

 The results are regarded as unreliable, since the extraction is very questionable. 



Determination of sugar by polarization. Filsinger. 4 13.024 grams are mixed with 

 water in a 100 cc flask. The solution is clarified with basic lead acetate, made up to 

 the mark, filtered, and polarized in a 200 mm tube. 



Mansfeld 5 . Ten grams of chocolate are heated with 100 cc water in a 250 cc flask 

 to 35 C., well mixed, clarified with lead acetate and alum, and made up to the mark. 

 The clear filtrate is polarized. 



Determination of sugar by inversion. Ass. Swiss Anal. Chem. 5 The substance is 



1 Op. cit., note 8, p. 938 of this work. 

 3 Op. cit., note 2, p. 951 of this work. 



3 Zipperer, Untersuch, u. Cacao u. dessen Priiparate, 1887 ; see also op. cit., note 8, 

 p. 938 of this work. 



4 Op. cit., note 7, p. 938 of this work. 

 6 Op. cit., note 1, p. 950 of this work. 



