Chemical and Physical Papers. 39 



ANALYSIS. 



In the analysis of coffee we have as yet no standard that would 

 estimate the value of coffee from the commercial standpoint. The 

 bureau of chemistry of the United States Department of Agricul- 

 ture, in its standard for this beverage, makes the following state- 

 ments : 



1. Coffee is the seed of Cofea arahica L. or Cofea liherica 

 Bull., freed from all but a small portion of its spermoderm, and 

 conforms in variety and place of production to the name it bears. 



2. Roasted coffee is coffee which by the action of heat has be- 

 come brown and developed its characteristic aroma ; it contains 

 not less than ten per cent, of fat and not less than three per cent. 

 of ash. 



In Bulletin No. 90 of the bureau of chemistry of the Depart- 

 ment of Agriculture, page 43, there are two processes mentioned 

 for the determination of caffeine and caffeotannic acid, which I 



hereby transcribe : 



Caffeine. 



Method of Hilger and Fricke {a). — Take 5 to 10 grams of coffee, 

 add 100 cc. of water, and boil, filter, and treat the residue twice 

 more with boiling water. Add to the united filtrates an excess of 

 lead acetate, filter, and wash. Treat the filtrate with hydrogen sul- 

 fid to remove the excess of lead, filter, wash, and evaporate the 

 filtrate to dryness in a Hoffmeister schalschen with some sand and 

 a little magnesia. Crush the schalschen between filter-paper, place 

 in a continuous-extraction apparatus, and extract with chloroform 

 until exhausted. Dry the chloroform extract at 100 degrees and 

 weigh as caffeine. If the caffeine does not appear to be pure, de- 

 termine the nitrogen in the residue by the Gunning method. 

 N X 3.464 = caffeine. 



Caffeotanic Acid. 



Krug's method {h). — Treat two grams of the coffee with 10 cc. 

 of water and digest for thirty-six hours, add 25 cc. of 90 per cent, 

 alcohol and digest twenty-four hours more, filter, and wash with 

 90 per cent, alcohol. The filtrate contains tannin, caffeine, color, 

 and fat. Heat the filtrate to the boiling-point and add a saturated 

 solution of lead acetate. If this is carefully done a caffetannate of 

 lead will be precipitated, containing 49 per cent, of lead. As soon 

 as the precipitate has become flocculent, collect on a tared filter, 

 wash with 90 per cent, alcohol until free from lead, wash with ether, 

 dry, and weigh. The precipitate has the following composition : 

 Pb3Ci5His082. The weight of the precipitate multiplied by 0.51597 

 gives the weight of the caffeotannic acid. 



