DETERMINATION OF THEOBROMINE. 953 
bath with continual stirring. The residue is extracted with CHCl; 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 
cafieine. The benzo] is distilled off, the residue shaken with water, and the solution 
filtered and evaporated. 
Weigmann.'—Twenty grams of the material are rubbed up into asoft 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 ce 
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.SO, (the liquid should contain at least 6 per cent H.SO,), 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 .*—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 until a drop of the filrate after cooling gives 
no precipitate with sodinm 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 H2,SO, and the lead sulphate separated by filtration. 
The filtrate is mixed with a large excess of sodinm 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 about6 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 to8 per cent H,SO,. The 
filter and precipitate are placed in a beaker and Ba(OH), added until the reaction is 
alkaline. Heating renders the decomposition more rapid. The excess of Ba(OH), is 
neutralized with H.,SO,, and any possible excess of the latter with BaCO3;. 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,)2COs, reignite and weigh. The difference is theobromine. 
Zipperer.*—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),. 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.*—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®.—Ten grams of chocolate are heated with 100 cc water in a 250 ce 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.’—The substance is 
1 Op. cit., note 8, p. 938 of this work. 
2 Op. cit., note 2, p. 951 of this work. 
*Zipperer, Untersuch, ti. 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. 
5 Op. cit., note 1, p. 950 of this work. 
