9 



however, is equally indicative of quinidin ; it gives scarcely any per- 

 ceptible reaction with quinicine. 



VIII. Pelletier's chlorine gas-test succeeds very well with the free 

 alkaloids, but does not show any indication with their salts. It is 

 equally capable of detecting quinidin, and gives the same phenomena. 



IX. Marchand's test is not a delicate reaction. 



X. All the foregoing tests, although specially proposed for the 

 discovery of quinine, possess equal powers and show the same ap- 

 pearances with quinidin. But they have no reaction on cinchonine, 

 cinchonidin, or cinchonicine. 



XI. Van Heijningen's test by oxalate of ammonia, produces, after 

 some hours, a crystalline oxalate of quinine, when using a fluid con- 

 taining only 1 grain of alkaloid in 800 grs. of water, and very 

 readily detects immediately 1 part in 350. It does not precipitate 

 quinidin or cinchonidin, but it produces a white precipitate in con- 

 centrated solutions of cinchonine. 



XII. De Vry's test for quinidin by hydriodic acid, or iodide of 

 potassium in neutral solutions, produces a well-marked crystalline 

 precipitate as a colourless salt, when one part of the alkaloid is 

 present in 1000 of the fluid; the crystals, being short hemihedral 

 prisms, are readily recognized ; the neutral hydriodates of cincho- 

 nidin are colourless, silky, prismatic needles, and much more soluble. 

 If to a solution of the sulphate of quinidin in dilute spirit (^) we 

 add hydriodic acid, and expose to the action of light during some 

 days, there is formed the red iodo-sulphate of the author. 



The neutral hydriodate of quinine appears as lemon-yellow prisms. 

 The neutral hydriodate of cinchonine appears as long, thick, colour- 

 less prisms, and is very soluble. 



XIII. Liebig's ether test dissolves quinine, quinicine, and cin- 

 chonicine, and therefore does not discriminate between them, as they 

 are all uncrystallizable. It dissolves also a portion of the quinidin 

 and ciuchonidin. Should the proportions of these alkaloids not ex- 

 ceed the solvent powers of the ether employed, they will not be indi- 

 cated by this test. When crystallization occurs, the rhombic prisms 

 indicate cinchonidin ; the long slender aciculse, quinidin ; whilst an 

 amorphous powder is demonstrative of cinchonine. Ether also ex- 

 tracts cinchonidin from cinchonine ; but its sparing solubility in ethe^ 

 necessitates the employment of warmth, and a large quantity of ether. 



