OS COFFEE. H5 



w ater : 2. a very small quantity of essential oil : 3. a resin raw coffee. 

 in tolerable abundance: 4. a gum in greater quantity: 5. 

 gallic acid, but no tannin: 6. extractive matter: 7. a little 

 albumen. 



Observations. 

 If the decoction filtered while hot become turbid on cool- General re- 

 ing, it i» because it holds in solution by means of the heat a mar son em * 

 little resin. Alkalis render it brown ; their usual effect on 

 vegetable decoctions. Lime water precipitates it, because 

 on the one hand gallate of lime is formed ; and on the other 

 the gummy extractive matter unites with the earth, and car- 

 ries it down., The same may be said of the sulphate of alu- 

 mine. Spirit of wine separates the mucilage, because gums 

 are not soluble in alcohol ; and water precipitates the alco- 

 holic tincture, because resins are insoluble in water. This 

 precipitate by water is white in consequence of its extreme 

 division : by sulphate of iron green, because it is mixed with 

 gallate of iron : by oxigenized muriatic acid fawn-coloured, 

 because the oxigen, attacking the resin, sets bare a little 

 carbon. The insoluble scum formed on the surface of th* 

 decoction is a little vegetable albumen coagulated by boiling 

 water. To obtain this, it is necessary, that the water should 

 stand some time on the coffee cold, before it is heated. 



Proportions by Approximation. 

 Though it is not of much use to inquire into the pro- Proportion* of 

 portions of the immediate principles of coffee, since these Jts P""^?^- 

 proportions must vary as the berry is more or less ripe, and 

 according to the place from which it comes, and the time it 

 has been kept, I have deemed it not superfluous, to esti- 

 mate them as nearly as may be. After several comparative 

 experiments I have found, that eight ounces of coffee afford 

 nearly 





oz. 



dr. 



gr- 



Of mucilage 



1 











Resin - 



- 



1 







Colouring extractive matter 







1 







Gallic acid - 



- 



3 



36 



Parenchyma 



5 



3 



36 



Vegetable albumen - 



- 







10 



7 1 10 



It 



