]20 ON COFFEE. 



Observations. 

 Effects of It follows from these experiments, that roasting develops 



roasring. ^ e 0( j oran t and resinous principles of coffee, and forms in 



it tannin, which is soluble only in cold water. This is a 

 very singular phenomenon. Gallic acid manifests itself in 

 coffee, at every temperature of the water employed as a 

 menstruum. The gum and colouring extractive matter are 

 more abundant in the decoction than in the infusions ; but 

 the aromatic principle is more perceptible and more agree- 

 able in the latter. 



Distilled Water of roasted Coffee. 



Water distilled I distilled several quarts of water from roasted coffee. 



from roasted The. wa ter was impregnated with the aroma of the coffee, 



. ' and carried over with it some atoms of concrete essential 



oil, like that obtained from the distillation of raiv coffee. 



Reagents did not demonstrate the presence of any substance 



in solution in this water. 



Infusions and Decoctions compared. 

 "Treated first To find the different solubility of the principles of coffeey 



•smh cold water ft remained for me to subject the same powder of roasted 

 coffee to the successive action of infusion and decoction* 

 For this purpose I placed in a filter two ounces of coffee, 

 and passed cold water through it, till the reagents ceased to 

 indicate the presence of the matters in solution. Sixty-eight 

 ounces of cold water were necessary to divest the coffee of 

 all the matter thus soluble. I divided this water into seven- 

 teen portions of four ounces each, as they passed through 

 the filter. All these contained gallic acid in proportion to 

 the order in which they passed through : the first four took 

 up gum ; but only the first indicated the presence of tannin, 

 by precipitating a solution of glue, 

 then with hot, The coffee having been taken out of the filtre, and dried 

 oft a stove, I poured on it eight ounces of water at 75^ 

 (201 ° F.) The smell of this secondary infusion was plea- 

 sant, but weaker than that of coffee prepared for the table. 

 Examined by reagents it furnished a little mucilage, and a 

 great deal of gallte acid ; but I found in it neither tannin 

 nor resin. 



I took 



