CHEMICAL CONSTITUENTS OF THE CINCHONA BARKS. 61 
The amount of water contained in air-dried Cinchona barks 
seals usually to from g to 11 per cent. (Compare also page 
34: 
The oldest observation which relates to the peculiar constituents 
of Cinchona barks, or at least to those which are characteristic of 
them, reverts to the year 1745, when Claude Toussaint Marot de 
Lagaraye, of Paris, perceived the deposit of a salt from an extract 
of Cinchona.t. S. F. Hermbstadt, of Berlin, in 1785, recognized 
therein the calcium compound of an acid, the peculiarity of which 
was established in 1790 by Friedr. Christian Hofmann, an apothe- 
cary of Leer, in Hanover, who named it chzmasdéure (kinic acid). 
Vauquelin, in 1806, determined more precisely the properties, 
and Liebig the composition, of kinic acid. It occurs in all true 
Cinchona barks, in amounts of as much as g per cent., and upon it 
depends the acid reaction of their aqueous extracts; it is, however, 
without any considerable physiological action. Hlasiwetz, in 1851, — 
found kinic acid also in the Cinchona nova, mentioned on page 49. 
Since, according to Hesse, it is absent in the Cinchona cuprea, it 
would be desirable to know its distribution in the group of the 
Cinchonez, the more so as it belongs to those plant acids which 
are of quite common occurrence. Kinic acid forms large, hard, 
monoclinic crystals, which are soluble in somewhat more than twice 
their weight of water. The solution is odorless, of a purely acid 
taste, not bitter, and deviates the plane of polarization to the left. 
According to its constitution, C,H,(OH), CO-OH, and that of its 
derivatives, the acid belongs to the class of aromatic compounds; 
by the action of hydriodic acid it may be reduced to benzoic acid 
and protocatechuic acid, and by energetic oxidation may be con- 
verted into quinone (or kinone). In closest relation to kinic acid 
stands the so-called acorn-sugar, or quercite, C,H,(OH),. 
In the barks of the Cinchonas and the most closely related Ru- 
biaceze, there is found an uncrystallizable bitter principle, c¢novzn’ 
1 Chymie hydraulique, sig extraire les sels essentiels des végétaux, animaux et miné- 
raux avec l'eau pure, par M. L. C. D. L.G._ (Monsieur le comte de la Garaye), Paris, 
1749, 114. The Count occupied himself with chemistry for philanthropic purposes. 
2 According to recent researches of Liebermann and Giesel, Berichte der Deutsch. 
Chem. Gesellschaft, 1883, pp. 926-941, the chinovin obtained from cinchona cuprea Is 
not identical with dacobtaln from the true cinchonas, but only isomeric therewith ; 
the former they designate as # chinovin, and the latter as a chinovin. Both substances, 
in a pure state, form a white, very loose, crystalline powder, but differ in their behavior 
to solvents and in some chemical reactions. Thus the §, in distinction from the @ chi- 
novin, is insoluble in absolute ether and in acetic ether, while the # compound is much 
more freely soluble in oon one lute wscurcungl™ ones by Pg eer have the — 
elemen composition, which is provisionally r ed by the authors as corresponding _ 
to the poh CH, 2031, while aa of chinovic acid is regarded as C,;,H,,O0,. The 
