ON COFFEE. 



119 



hoi separated more gum from it than from the cold infuv. 

 sion. The three sorts of coffee comported themselves the 

 same in these experiments. 



Decoction. 

 I boiled two ounces of powdered coffee in one pound boiled. 

 of water, and continued the boiling for two hours. The 

 smell of the decoction was infinitely less agreeable and aro- 

 matic than that of the infusion. It did not change the co- 

 lour of blue paper, or precipitate the solution of gelatine, 

 but was blackened by sulphate of iron. Alcohol separated 

 from it much more mucilage than was found in the infusions, . 

 in proportion to the quantity of coffee. The three sorts of 

 coffee afforded the same results. 



If a filtered and limpid decoction of coffee be boiled a Effect of long 

 long time exposed to the air, it grows turbid, and deposits D0llin S* 

 a black powder, which has sometimes been mistaken for 

 resin, but is only extractive matter highly oxigenized. Phy- 

 sicians arid apothecaries have not yet sufficiently examined 

 the action of the air on vegetable decoctions ; but they might 

 derive from it some information respecting the more or less 

 active properties of certain medicines. 



Extract of Coffee. 

 The decoction of coffee, when filtered an£ evaporated Extract. 

 to the consistence of an extract, has no longer the aromatic 

 odour of the infusion. Its taste is bitter. Heated with 

 alcohol, this extract colours .it with its extractive matter, 

 but the tincture affords no precipitate on the addition of 

 water. Hence we may conclude, that the decoction of 

 coffee, after it has been filtered or stood to settle, contains 

 no resin. 



Spirituous Tincture of roasted Coffee. 

 Roasted coffee digested in alcohol affords a high coloured Tincture, 

 tincture, from which water precipitates a larger quantity TO^tetTthan 11 

 of resin, than from the tincture of dry or raw coffee. — ■ raw coffee. 

 From the latter the resin is white : from the tincture of 

 roasted coffee it is fawn coloured. 



Observations 



