956 FOODS AND FOOD ADULTERANTS. 



Determination of water-in sol idle organic matter. Beusemann. 1 Two grams of the 

 substance are covered with cold water and allowed to stand twelve hours, with 

 occasional stirring. The insoluble residue is collected, washed cold, dried at 100 

 C., weighed, incinerated, and weighed again. Difference^ weight of water-insoluble 

 organic matter. 



Determination of gum. Boussingault. 2 An aqueous infusion of the fat-free material 

 is precipitated with alcohol. 



Determination of nitrogen. Mansfeld 3 used Kjeldahl's method, starting with 3 

 grams of material. 



Determination of coloring matter and tannin. Mansfeld. 3 The residue from the fat 

 determination (see page 951) is extracted with 80 per cent alcohol. In this extract 

 sugar, theobromine, and total residue are determined. Total residue (sugar + 

 theobromine) = coloring matter and tannin. 



Detection of the use of fixed alkalis and ammonia in the process of manufacture of 

 cocoas. Stutzer. 4 The total ash, ash soluble in water, total PaO 5 and PiO fi soluble 

 in water are determined. The relative proportions of these constituents in the ash 

 of a normal cocoa and in the ash of cocoas treated with fixed alkalis and ammonia 

 are given in the table on page 943. Additional evidence of the use of ammonia is 

 obtained by distillation of the sample with magnesia and determination of the am- 

 monia in the distillate. If this process yields more than 0.1 per cent of nitrogen in 

 the form of ammonia, this writer considers the result certain evidence of the use of 

 ammonia, or ammonia salts, in the process of manufacture. 



METHODS BY WHICH THE RESULTS GIVEN IN THE TABLE ON PAGE 



980 WERE OBTAINED. 



The methods outlined below were chosen as best suited for the pur- 

 pose. While some are only approximate methods, they are sufficiently 

 accurate for the purpose and are much more rapid than some of the 

 methods previously employed. 



Microscopical examination. The method used for the preparation of the sample for 

 the microscopical examination has been outlined on page 949. 



Determination of moisture, ash, and of the amount of acid required to neutralize the ash 

 from two grams of material. Two grams of material are distributed over the bot- 

 tom of a flat platinum dish and dried to constant weight at 100 to 105 C. The 

 loss = moisture. The residue is carefully ignited in a muffle and weighed for the 

 amount of ash. The ash is then washed into a beaker, dissolved, with gentle boiling, 



N N 



in H 2 SO 4 , and the excess of acid determined by titration with NaOH. Cc of 



N N 



H 2 SO 4 cc of NaOH = the number given in the table on page 980 as "acid 



equivalent." 



Determination of fat. Three grams of the substance are placed in a 300 cc flask 

 and covered with 200 to 250 cc of redistilled petroleum ether ; after standing 4 to 

 5 hours with occasional shaking, the flask is filled nearly to the mark with petroleum 

 ether, shaken, and allowed to stand over night. After making up to the mark and 

 thorough shaking, the insoluble portion is allowed to deposit; the supernatant liquid 

 is then quickly decanted into a 100 oc flask until, the latter is just filled to the 

 mark, using every precaution to avoid raising the temperature of either flask. This 

 portion of 100 cc is filtered through a Gooch crucible, and the slight residue washed 



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

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

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

 *Op. cit., note 3, p. 939 of this work. 



