952 FOODS AND FOOD ADULTERANTS. 



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 adul- 

 teration with waxes, stearin, paraffin, and beef tallow. The taste, odor, melting point, 

 and ether test are 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 N B OH, when the 

 stearic acid goes into solution as stearate of sodium and is reprecipitated by H. 2 SO.|. 



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 decoc- 

 tion obtained with basic acetate of lead. After removing the excess of lead with 

 H. 2 S, evaporate to dryness and exhaust the residue with boiling alcohol. On cool- 

 ing this solution the alkaloid separates out as a crystalline powder. 



HassalP 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 hun- 

 dred 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 evapo- 

 rated to dryness for weight. 



Legler' 1 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 H 2 SO 4 . The solution is filtered and the theobromine precipitated with 

 sodium phosphomolybdate. After standing twenty-four hours, filter, wash with 6 to 

 8 per cent H. 2 SO 4 , and dissolve the precipitate in NaOH or Na^COs. Add sufficient 

 H 2 SO 4 to the solution to leave it slightly alkaline, evaporate with sand, dry at 110 

 C., and extract at 70 to 90 C., with aniyl. alcohol. Evaporate the extract to dry- 

 ness 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 CHC1 3 . The extract is evaporated to dry- 

 ness and the residue dissolved in boiling water. The solution is filtered, evaporated 

 to dryuess, and the residue of theobromine weighed ; the alkaloid thus obtained is 

 pure. 



Mulder. 7 Ten grams of cocoa are rubbed to a paste with water and boiled for fifteen 

 minutes; some MgO is uowaddedand the mixture evaporated to dryness on the water 



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



2 Op. cit., note 2, p. 936 of this work. 

 " Op. cit., note 3, p. 936 of this work. 

 4 Op. cit., note 2, p. 941 of this work. 



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



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



7 Op. cit., not* 8, p. 938 of this work. 



