956 FOODS AND FOOD ADULTERANTS. 
Determination of water-insoluble organic matter.—Bensemann.'—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? used Kjeldahl’s method, starting with 3 
grams of material. 
Determination of coloring matter and tannin.—Mansfeld.’—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.+—The total ash, ash soluble in water, total P,O; and P.O; 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, 
oe H,.SO,, and the excess of acid determined by titration with 1) NaOH. Ce of 
—H,SO, — ce of 7, 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 ce 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 ce 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 ce is filtered through a Gooch crucible, and the slight residue washed 
1 Op. cit., note 4, p. 949 of this work. 
2 Op. cit., note 2, p. 941 of this work. 
3 Op. cit., note 1, p. 950 of this work. 
4 Op. cit., note 3, p. 939 of this work. 
