CINCHONA 



639 



place. (2) If one drop of the neutral solution be mixed with four drops 

 of water and a drop of bromine water, followed by a drop of a solution 

 of ferrocyanide of potassium, and then an excess of ammonia water, a 

 red coloration is immediately produced, which disappears shortly. 



Constituents. The alkaloids are chiefly formed in the paren- 

 chyma cells of the middle layers of the bark. Cinchona contains 

 a large number of alkaloids, of which the most important are quinine, 

 quinidine, cinchonine and cinchonidine. The total alkaloids amount 

 to about 6 or 7 per cent, of which from one-half to two-thirds is qui- 



FIG. 284. Cinchonine sulphate: Orthorhombic crystals from a saturated aqueous 



solution. 



nine in the yellow barks, whereas, in the red barks, cinchonidine 

 exists in greater proportion. QUININE occurs in small crystals 

 which are sparingly soluble in water, soluble in alcohol and readily 

 form crystallizable salts with acids. On the successive addition of 

 dilute sulphuric acid, bromine or chlorine water and ammonia water, 

 the solution becomes of an emerald-green color (thalleioquin test). 

 QUINIDINE, an isomer of quinine, crystallizes in rhombohedra or 

 monoclinic prisms which are nearly insoluble in water and otherwise 

 conforms to the characteristics given for quinine. The solutions of 

 quinidine are, however, dextrorotatory, while those of quinine are 



