13S Experiments vpon the 



I ought to sav, however, that if cinchona be reduced to 3 

 fine powder, and repeatedly exposed to the action ot alcohol 

 assisted by heat, there remains little for the acids to do. The 

 substance extracted from cinchona by the acids is, to all ap- 

 pearances, of the same nature as that which is dissolved in 

 alcohol; as I shall soon explain. 



The nitric acid acquires by this combination a colour in- 

 clining to red, sometimes orange : but lliese shades vary 

 much in intensity, according to the Concentration of the 

 acid ; they change to the yellow so iDUch the more as the 

 acid is more concentrated. The nitric acid by this com- 

 bination loses much of its acidity, at least the taste seems to 

 announce this : it is true that this acid dissolves at the same 

 time a certain quantity of lime, which the oxalate of am- 

 monia demonstrates, and this substance contributes its share 

 in neutralizing it. 



If we pour into this nitric solution saturated carbonate of 

 potash, a precipitate of a fine red colour is formed ; but if 

 we employ the common carbonate, and an excess of it is 

 added, the colour of the precipitate changes to violet, purple, 

 or blue. Thus the alkalis have the property of changing 

 into blue the colour of these kinds of cinchonas, which is 

 red in its nature. 



The metallic solutions form there also precipitates va- 

 riously coloured, and more or less considerable as the nitric 

 acid contains more or less vegetable matter ; but, on sa- 

 turating the excess of acid, the metallic salts then pro- 

 duce very abundant precipitates, and the liquor is disco- 

 loured. 



1. The solution of muriate of tin occasions a red or flesh- 

 coloured precipitate. 



9.. That of sulphate of iron, a grayish precipitate. 



3. That of copper, a chestnut-brown precipitate. 



4. The sulphale of titanium, assisted l)y a little carbonate 

 of soda, formed in the nitric solution of cinchona an orange 

 red precipitate, analogous in its shade to that which gall- 

 niils produce in the solutions of this inetal. 



5. Alum causes no change in the acid solution of cin-r 



3 chona^ 



