154 METHODS OF ANALYSIS. 



remove the excess of lead, filter, wash, and evaporate the filtrate to dryness in 

 a Hoffmeister Schalchen with some sand and a little magnesia. Crush the 

 schalchen between the filter paper, place in a continuous extraction apparatus, 

 and extract with chloroform until exhausted. Dry the chloroform extract at 

 100 C. and weigh as caffein. If the caffein does not appear to be pure, deter- 

 mine nitrogen in the residue by the Kjeldahl or Gunning method ; multiply the 

 amount of nitrogen found by 3.464 to^ obtain the amount of caffein present. 



17. Crude Fiber. 



Proceed as directed under " VI. General Methods," page 56. 

 18. Crude Starch by Direct Inversion. 



Use 4 grams of the sample and proceed as directed under " VI. General 

 Methods," page 53,. section 8 (a). 



19. Starch. 



Use 4 grams of the sample and employ the diastase method as given on page 

 53, under "VI. General Methods," section 8 (b). 



20. Sucrose. 



Use half the normal weight and proceed as directed under " VI. General 

 Methods," page 40, section 6 (c). 



21. Reducing- Sugars. 







Use 100 cc of the solution prepared as directed under " 7. Soluble Solids," 

 and proceed as directed under "VI. General Methods," page 42, section 7 (a). 

 Calculate results as dextrose. 



22. Petroleum Ether Extract. 



Dry 2 grams of coffee at 100 C., extract with petroleum ether (boiling point 

 35 to 50 C.) for 16 hours, evaporate the solvent, dry the residue at 100 C., 

 and weigh. 



23. Ten Per Cent Extract McGill Method. 



Weigh into a tared flask the equivalent of 10 grams of the dried substance, 

 add water until the contents of the flask weigh 110 grams, connect with a 

 reflux condenser and heat, beginning the boiling in 10 to 15 minutes. Boil for 1 

 hour, cool for 15 minutes, weigh again, making up any loss by the addition of 

 water, filter, and take the specific gravity of the filtrate at 15 C. 



According to McGill, a 10 per cent extract of pure coffee has a specific gravity 

 of 1.00986 at 15 C., and under the same treatment chicory gives an extract with 

 a specific gravity of 1.02821. In mixtures of coffee and chicory the approxi- 

 mate percentage of chicory may be calculated by the following formula : 



(1.02821-sp.gr.) 

 Per cent of chicory =100 001835 



The index of refraction of the above solution may be taken with the Zeiss 

 immersion refractometer or with the Abbe refractometer. 



With a 10 per cent coffee extract, n D 20 =1.3377. 



With a 10 per cent chicory extract, n D 20=1.3448. 



Determinations of the solids, ash, sugar, nitrogen, etc., may be made in the 

 10 per cent extract, if desired. 



