various species of Cinchona. 133 



stance acts wUli water is, that if only a small quantity of 

 this fluid is employed, it is entirely dissolved, and furnishes 

 a clear liquor ; if more water is afterwards added it becomes 

 turbid, and latterly becomes clear again upon the addition 

 of a still greater quantity of this fluid. 



It would seem, according to this, that there is in it an- 

 other body, which, when it is concentrated, favours its so- 

 lution; and that this body afterwards loses this property upon 

 being diluted in water. 



It is this matter which, by separating itself, makes turbid 

 such infusions of cinchona as are prepared by heat, as well 

 as the macerations evaporated to a certain degree. This is 

 what has been designated by chemists under the name of 

 resin of cinchona: its solution in water becomes mouldy in 

 a few days, and forms a fungus like a solution of gum ; 

 which proves that it is not a true resin, as this last never 

 grows mouldy. 



The aqueous solution of this substance recently prepared, 

 and a little concentrated, presented the following effects 

 with the different agents mentioned: 



1 . With ammonia it coagulates into a thick whitish mat- 

 ter, which becomes brown in the air, and hardens consi- 

 derably a short time afterwards ; but it becomes soft when 

 healed, and assumes the ductility and dirty lustre of turpen- 

 tine wrought throusrh the hands. 



2. It produces nearly the same phaenomena with the alka- 

 line carbonates. 



3. The ordinary acids produce no sensible change upon 

 it ; the oxymuriatic acid makes it yellow, without producing 

 any precipitate ; but if we afterwards mix ammonia with it, 

 there is a grayish white precipitate formed, which is light 

 and flaky. 



4. The solution of animal gelatine does not precipitate it 

 at all ; the infusion of these kinds of cinchona, however, 

 precipitates the solution of animal glue : the principle which 

 produces this effect must therefore be altered during the eva- 

 poration. 



5. The muriate of iron, or any other ferruginous salt, pro- 



I 4 duces 



