Mulder.7 - Ten grams of cocoa are rubbed to a paste with water and boiled for fifteen minutes; some MgO is now added and the mixture evaporated to dryness on the water bath with continual stirring. The residue is extracted with CHC13 and the chloroform distilled off. The residue is dissolved in hot water, the solution filtered, evaporated 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.

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

2 Op. cit., note 2, p. 936 of this work. 3 Op. cit., note 3, p. 936 of this work. 4 Op. cit., note 2, p. 941 of this work. 5 Op. cit., note 2, p. 940 of this work.

6 Ber. d. Chem. Ges., 15, 2938; Zeitsch. f. anal. Chem., 23,89.

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

Weigmann.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 minutes. 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 precipitate is filtered off, the filtrate concentrated on the water bath, strongly acidulated with H2S04 (the liquid should contain at least 6 per cent H2S04), 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 until a drop of the filrate after cooling gives no precipitate with sodium phosphomolybdate. A volume of 700 to 800 cc is generally necessary. After the addition of NaOH, the filtrate is evaporated to 50 cc. It is then strongly acidulated with H2S04 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 H2S04. 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 H2S04, and any possible excess of the latter with BaC03. 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 (NH4)2C03, 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 dryness on the water bath with 15 grams of Ca (OH)2. The dry residue is extracted with CHCL3, 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.

Mansfeld5. - 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 extracted with water; the extract is evaporated to a sirupy consistency, treated with alcohol, decolorized by means of lead acetate, the excess of which is removed with H2SO4. The sugar thus prepared is inverted and the invert sugar determined with Fehling's solution.

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

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

3 Zipperer, Untersuch, u. Cacao u. dessen Praparate, 1887; see also op. cit., note 8, 938 of this work.

4 Op. cit., note 7, p. 938 of this work. 6 Op. cit., note 1, p. 950 of this work.

Hassall.1 - The sugar is dissolved out of the sample with cold water, inverted by boiling with dilute H2S04, and then estimated with copper solution.

Mansfeld.2 - The residue from the fat determination is extracted for three hours with 100 cc of 80 per cent alcohol, and the extract made up to 150 cc. Fifty 00 are evaporated to dryness. After weighing, the residue is dissolved in water, made up to 100 cc, heated one-half hour on the water bath with 10 cc N /2 HC1, neutralized with NaOH, and diluted to 250 cc. The invert sugar is then gravimetrieally determined with Fehling's solution.

Determination of sugar by direct weighing. - Hassall.1 - Dissolve a weighed quantity of cocoa containing sugar in cold water and collect the residue on a filter. This residue is dried on the water bath and weighed.

100 - per cent of insoluble matter=:per cent of soluble matter. Per cent of soluble matter - (per cent of moisture the approximate per cent of soluble matter in cocoa) = per cent of sugar.4 w

Herbst.3 - The residue from the fat determination is extracted with boiling 50 per cent alcohol as long as the extract is colored. This extract is evaporated to dryness and treated with cold water, which dissolves the sugar. This solution .is evaporated to dryness, the residue dried in hydrogen and weighed.