13-1 Experiments upon the 



It" we allow tlie infusions of cinchona to cool several times 

 before reducing them to dryness, they deposit upon each 

 cooHng a matter similar to that of which we have spoken. 

 It was formerly thought that this substance became insoluble 

 on its combination with oxygen; but this eflect seems to be 

 owing to the insufficiency of the water. 



It is (his resinous kind of matter which gives to cinchonasi 

 and their infusions the bitter taste they possess; for, if we ■ 

 separate the deposits as they are formed, and afterwards di- 

 lute the concentrated matter with the same quantity of water, 

 the liquor has no longer any thing like the same degree of 

 bitterness'. Nevertheless, the whole of this substance is not 

 separated from the water by this means ; the other principles 

 of cinchona always retain a tolerably large quantity of it in 

 solution. 



But if, after having performed the various operations in 

 the manner I have described, we treat with alcohol the in- 

 fusions of cinchona reduced into the form of soft extract, 

 and separate the greatest part of the resinous-formed matter, 

 there remains nothing but a viscous substance of a brov/n 

 colour, wlilch has hardly any bitter taste, which is com- 

 pletely soluble in water, and does not precipitate on cooling. 



These experiments teach us, that in the infusions of these 

 kinds of cinchona tliere arc at least two very distinct sub- 

 stances ; the one bitter and astringent, soluble in alcohol, 

 little soluble in water; the other, on the contrary, absolutely 

 insoluble in alcohol, very soluble in water, having a sweet 

 and mucilaginous taste. 



These substances being without doubt those which act the 

 ■most efficaciously in maladies where cinchona is employed, 

 I think it right to explain their properties in detail : I shall 

 commence with that which is soluble in alcohol, 



1. This substance, in the dry state, has a brownish red 

 colour and an extremely bitter taste. 1. Cold water only 

 dissolves a part of it; the rest remains in the form of reddish 

 flakes ; but if we heat the mixture the latter dissolve also, 

 and we obtain a clear liquor of a very deep red, which be- 

 comes turbid on cooling, but deposits very little. 



What is remarkable in the manner in which this sub- 

 stance 



