DETERMINATION OF FIBER. 955 



cc water are added. The mixture is slowly heated to 70 to 80 C. and kept at that 

 temperature for one-half hour. After completely cooling the Cu 3 O is collected on a 

 filter, washed cold, dried at 100 to 110 C., and weighed. 



1 gram Cu 2 O = 0.45315 grams of starch. 



Hassall ' gives a method similar to that of the Ass. Swiss. Anal. Chem. given above. 



Mansfeld. 2 Two portions of 25 grams of cocoa, or 5 grams of chocolate, are 

 weighed out and placed in 250 cc flasks with 100 cc of water in each. One sample is 

 heated ou the water bath; the other is placed in. water at 30 to .40 C., and shaken 

 to emulsify the fat. After thirty minutes the cooled samples are shaken with 50 cc 

 of a standard solution of Ba(OH) 2 and 45 per cent alcohol added until the liquid 

 reaches the mark. Cool and make up with similar alcohol if necessary. The 

 Ba(OH)^ solution is titrated by mixing 50 cc with 100 cc of water and making up 

 to 250 cc with 45 per cent alcohol, using N/| HC1 with phenolphthalein for an indi- 

 cator, and titrating 50 cc. The sample is allowed to settle, and 50 cc of the yellow 

 supernatant liquid titrated. The difference between these two titrations for pure 

 chocolate is 1.25 cc. The general increase for each per cent of flour is 0.3 cc. Hence : 



X - 10 Q- . D = number of cubic centimeters difference between the amounts of 



o 



N/io HC1 required. X = per cent of foreign starch in the sample. 



Mansfeld. 3 The residue left after the removal of petroleum ether and alcohol 

 extracts is dried and mixed with 500 cc of water; the mixture is heated for 

 one-half hour, on the water bath, diluted to 1,000 cc, cooled to 55 C., and mixed 

 with 0.1 gram of Liutner's diastase, which has been previously rubbed up with a 

 little water. Keep at 55 to 60 C. until iodine gives no reaction for starch, decant 

 into a 1,500 cc flask and make up to the mark. Heat 100 cc of the clear liquid 

 with 10 cc HC1, sp. gr. 1.125 for three hours on the water bath, cool, neutralize, 

 dilute to 500 cc and determine the dextrose gravimetrically. 



Schroeder. 4 For the inversion of the starch, 3 grms. of the material with 50 cc of 

 water and 1 cc HC1 (38.8 per cent) are heated for 1 hour under a pressure of one atmos- 

 phere. Results of experiments are also reported to show that this treatment does 

 not convert an appreciable amount of cellulose into dextrose. 



Weigmaun 5 uses diastase solution prepared as directed by Stutzer. Ten grams of 

 cocoa, deprived of fat. are boiled one quarter hour with water and made up to 500 cc; 

 250 cc are removed after shaking, treated with 2 cc of diastase solution for four 

 hours at 60 C., inverted with 20 cc HC1, neutralized and precipitated with lead 

 acetate. After removal of the excess of lead with H.jSO,, the nitrate is made up to 

 500 cc and the reducing sugar determined gravimetrically. 



Detection of Jtour in cocoa preparations. Reinsch. 6 Boil one part of the material 

 with ten parts of water, cool and filter. If the sample is pure it will filter rapidly, 

 give a clear filtrate, having a light reddish color, and leave a residue that is not 

 gummy. If flour has been added, it filters murky and slowly, and a gummy mass 

 remains on the filter. 



Determination of fiber. Ass. Swiss Anal. Chem. 7 used Henneberg and Stohmau's 

 method. This, as well as a method given by Mansfeld, does not differ materially 

 from the official method of the Association of Official Agricultural Chemists, an out- 

 line of which is given on page 958. 



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



-Zeitsch. f. Nahrungsmittel-untersuchung ii. Hygiene, 1888, 1, 2; Deutsch. Chem. 

 Ztg., 3, 91. 



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



4 Zeitsch. f. augen. Chem., 1892, 173. 



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



6 Further Gewerbe Ztg., 1868, 63; Zeit. f. anal. Chem., 8, 514. 

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



