METHODS OF COCOA ANALYSES. 951 



Mausfeld. 1 Five grams of cocoa, or 10 grains of chocolate, are mixed with au equal 

 weight of sand and extracted in a Soxhlet apparatus with petroleum ether. 



Wolfram 2 uses petroleum ether for the extraction of the fat. 



Qualitative examination of the fat.* The Association of Swiss Analytical Chemists 4 

 recommends the determination of the melting point by Riihdorfs method, Hiibls' 

 iodine number, and Kottstorfer's sapouification number. Bjorklund's ether test and 

 Filsinger'a ether-alcohol test are also stated to be of value. 



Bjorklund 5 covers about 3 grams of the fat in a test tube with double its weight of 

 ether, closes with a cork, and tries to bring the mass in solution by shaking at 

 18 C. When wax is present, a cloudy solution results, which is not changed by 

 warming. If the solution is clear, the tube is placed in water at C. and the time 

 observed after which the solution begins to become milky or to deposit white flakes ; 

 then the temperature is noted at which the mixture becomes clear on removing from 

 the water. When the solution becomes cloudy after ten to fifteen minutes and at 19 

 to 20 C. is again clear, the cocoa butter is pure. For a cocoa butter containing 5 per 

 cent of beef tallow, these numbers are eight minutes and 22 C. ; 10 per cent tallow, 

 7 minutes and 25 C., etc. 



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, Bjorkluud's ether test or Filsinger's ether-alcohol test may 

 be applied. This writer has modified the ether test as follows : 2 grins, of fat are 

 melted in a graduated tube with 6 cc. ot 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 test 8 is conducted as follows: About 1 gram of cocoa butter is 

 warmed with 2 to 8 grams of anilin until dissolved ; the mixture is allowed to stand 

 1 hour at 15 C., or ! to 2 hours, when temperature is 17 to 20 C. Pure cocoa butter 

 floats as a liquid layer on the auilin. If the cocoa contains tallow, stearic acid, or 

 a little paraffine, cloddy particles, which remain hanging ou 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. 



2 Jahresbericht d. k. chein. Centralstelle f. off. Gesundheitspflege in Dresden, 

 1878; Zeitsch. f. anal. Chein., 18, 346. 



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



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



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



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

 Chem., 23, 567. 



'Zeitsch. f. anal. Chem., 19, 247 ; Chem. Ztg., 1889, 13, 309 ; see also op. tit., note 2, p. 

 938 of this work. 



8 Zeitsch. 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. 



