COFFEE. 

 24. Caffetannic Acid Krug's Method. 



155 



Treat 2 grams of the coffee with 10 cc of water and digest for 36 hours; 

 add 25 cc of 00 per cent alcohol and digest 24 hours more, filter, and wash with 

 .o JUT cent alcohol. The filtrate contains tannin, caffein, 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: PbaCCwHisOsh. 

 The weight of the precipitate multiplied by 0.51597 gives the weight of the 

 caff eta imic acid. 



25. Megascopic Examination of Ground Coffee. 



Roasted cereals have a glossy appearance entirely different from that of 

 roasted coffee, and if roasted legumes are present, fragments of the hulls may be 

 seen. Mix a portion of the sample with cold water; fragments of pure coffee, 

 if not overroasted, will float, while common adulterants will sink. Examine 

 the latter microscopically. 



26. Microscopic Examination of Ground Coffee. 

 Examine for cereals, chicory, etc. 



U. S. Dept. Agr., Dirision of Chemistry, Bui. 13, Part 7, p. 908. 

 87404 Bull. 10709 12 



