Dieterich.6 - Equal parts of the fat and paraffin are melted together, a drop of the mixture placed on a slide and covered with a cover glass. After twelve hours this is examined with a power of 20 diameters and polarized light, at a temperature not exceeding 5° C. Pure cocoa butter shows palm-leaved crystals; 10 per cent of tallow, circular group of crystals.

Filsinger.7 - The iodine and Kottstorfer's numbers are determined in the dried fat. If these leave any doubt, Bjorklund's ether test or Filsinger's ether-alcohol test may be applied. This writer has modified the ether test as follows: 2 grms. of fat are melted in a graduated tube with 6 cc. of a mixture of 4 volumes of ether (sp. gr. 0.725) and 2 volumes of alcohol (sp. gr. 0.810), shaken and set aside. The pure fat gives a solution that remains clear.

Hager's anilin test8 is conducted as follows: About 1 gram of cocoa butter is warmed with 2 to 8 grains of anilin until dissolved; the mixture is allowed to stand 1 hour at 15° C, or 1 1/2 to 2 hours, when temperature is 17° to 20° C. Pure cocoa butter floats as a liquid layer on the anilin. If the cocoa contains tallow, stearic acid, or a little paraffine, cloddy particles, which remain hanging on the upper wall, on gentle agitation are deposited in the oil layer; if wax or much paraffin is present, the oil layer solidifies; if much stearic acid is present, there will be no separation into two layers, but the whole solidifies to a hard crystalline mass; with pure cocoa butter, the oil layer hardens only after many hours. A parallel test should be made with pure cocoa butter.

Hassall.9 - Melting point is determined. Foreign fats become rancid and tallowy in a few days.

Herbst.10 - Melting point determination and Bjorklund's ether test are recommended.

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

2Jahresbericht d. k. chem. Centralstelle f. off. Gesundheitspflege in Dresden, 1878; Zeitsch. f. anal. Chem., 18, 346.

3 See table on page 938 for the chemical and physical constants for cocoa butter.

4 Op. cit., note 3, p. 949 of this work.

5 Zeitsch. f. anal. Chem., 3, 233; see also op. cit., note 2, p. 938 of this work.

6 Geschafts-Ber. d. Papier- u. chem. Fabrik in Helfenberg, 1883; Zeitsch. f. anal. Chem., 23, 567.

7Zeitsch. f. anal. Chem., 19,247; Chem. Ztg., 1889,13, 309; see also op. cit., note 2, p. 938 of this work.

8Zeitsch. f. anal. Chem., 19, 246; see also op. cit., note 2, p. 938 of this work.

9 Op. cit., note 2, p. 940 of this work.

10 Op. cit., note 4, p. 950 of this work.

The small quantity of sesame oil, added to give the broken surface of chocolate a smooth appearance, can not be detected with certainty.

Mansfeld.1 - The purity of the fat is determined according to Filsinger. The melting point is determined according to Pohl.

Schaedler.2 - The comparatively high commercial value of cocoa butter brings adulteration with waxes, stearin, paraffin, and beef tallow. The taste, odor, melting point, and ether test arc mentioned as means of detecting foreign fats. Paraffin gives cocoa butter a soapy feel and lowers the specific gravity. An addition of stearic acid is made known by the high melting point and by boiling with dilute NaOH, when the stearic acid goes into solution as stearate of sodium and is reprecipitated by H2SO4.

Determination, of theobromine. - Blyth.3 - This author outlines the methods of Wosk-ressnsky, Mitscherlich, and Wolfram. He also gives the following "speedy method of determining, with fair exactitude, the per cent of theobromine in cocoa": Weigh out a definite portion and exhaust it with petroleum ether. Mix the residue with a little burnt magnesia and water, evaporate to dryness at 60° to 70° C, and exhaust the residue with boiling 80 per cent alcohol, which dissolves out the theobromine. After driving off the alcohol, the residue may be purified for weighing by washing with petroleum ether.

Boussingault.4 - Extract the sample with boiling water and precipitate the decoction obtained with basic acetate of lead. After removing the excess of lead with H2S, evaporate to dryness and exhaust the residue with boiling alcohol. On cooling this solution the alkaloid separates out as a crystalline powder.

Hassall5 uses the method devised by Hehner for the estimation of caffeine in tea, which is conducted as follows: Twenty grams of material are boiled with about a liter of water, cooled, and the solution made up to the mark and filtered. Five hundred cc of the clear filtrate are evaporated on the water bath with the addition of a little MgO. The dry residue is extracted with boiling alcohol. The united extract is evaporated nearly to dryness, taken up with ether, filtered, and evaporated to dryness for weight.

Legler" gives the following modification of Wolfram's method: 20 to 25 grams of cocoa, or 50 grams of chocolate, deprived of fat, are digested several hours with 4 per cent H2SO4. The solution is filtered and the theobromine precipitated with sodium phosphomolybdate. After standing twenty-four hours, filter, wash with 6 to 8 per cent H2S04, and dissolve the precipitate in NaOH or Na2C03. Add sufficient H2S04 to the solution to leave it slightly alkaline, evaporate with sand, dry at 110° C, and extract at 70 to 90° C, with amyl. alcohol. Evaporate the extract to dryness in a platinum dish, dry, and weigh. Ignite the residue and weigh again. The difference is the weight of the theobromine.

Mansfeld.1 - Another portion of 50 cc of the alcoholic extract, obtained by the author's method for the determination of sugar (see methods for determination of sugar on page 954), is evaporated to dryness with MgO and the finely powered residue extracted in a Soxhlet's apparatus with CHC13. The extract is evaporated to dryness and the residue dissolved in boiling water. The solution is filtered, evaporated to dryness, and the residue of theobromine weighed; the alkaloid thus obtained is pure.