y funnel, washing with cold water. Extract four times
with 25 cc. of chloroform. Evaporate the chloroform extract from a
weighed flask with aid of an air blast and dry at 100 deg. C. to constant
weight (one-half hour is usually sufficient). Weigh the residue as
caffein and calculate on 7.5 grams of coffee. Test the purity of the
residue by determining nitrogen and multiplying by 3.464 to obtain
caffein.

15. _Caffein--Power-Chestnut Method--Official_

Moisten 10 grams of the finely powdered sample with alcohol, transfer to
a Soxhlet, or similar extraction apparatus, and extract with alcohol for
8 hours. (Care should be exercised to assure complete extraction.)
Transfer the extract with the aid of hot water to a porcelain dish
containing 10 grams of heavy magnesium oxid in suspension in 100 cc. of
water. (This reagent should meet the U.S.P. requirements.) Evaporate
slowly on the steam bath with frequent stirring to a dry, powdery mass.
Rub the residue with a pestle into a paste with boiling water. Transfer
with hot water to a smooth filter, cleaning the dish with a
rubber-tipped glass rod. Collect the filtrate in a liter flask marked at
250 cc. and wash with boiling water until the filtrate reaches the mark.
Add 10 cc. of 10-percent sulphuric acid and boil gently for 30 minutes
with a funnel in the neck of the flask. Cool and filter through a
moistened double paper into a separatory funnel and wash with small
portions of 0.5-percent sulphuric acid. Extract with six successive
25-cc. portions of chloroform. Wash the combined chloroform extracts in
a separatory funnel with 5 cc. of 1-percent potassium hydroxid solution.
Filter the chloroform into an Erlenmeyer flask. Wash the potassium
hydroxid with 2 portions of chloroform of 10 cc. each, adding them to
the flask together with the chloroform washings of the filter paper.
Evaporate or distil on the steam bath to a small volume (10-15 cc.),
transfer with chloroform to a tared beaker, evaporate carefully, dry for
30 minutes in a water oven, and weigh. The purity of the residue can be
tested by determining nitrogen and multiplying by the factor 3.464.

16. _Crude Fiber--Official_

Prepare solutions of sulphuric acid and sodium hydroxid of exactly
1.25-percent strength, determined by titration. Extract a quantity of
the substance representing about 2 grams of the dry material with
ordinary ether, or use residue from the determination of the ether
extract. To this residue i