CINCHONA. 261 



cent, of quinia; pale bark, 0*7 to 1-4 per cent, of alkaloids, 

 chiefly cinchonia or quinidia with a little quinia ; the best red 

 bark, 2'6 per cent, of quinia, and 1-5 per cent, of cinchonia. 



2 and 3. The acids of cinchona. a. Kinic or q//i//i 

 CyH^Og, occurs in large colourless prisms, soluble in water. 

 In the bark it is probably combined with the alkaloids, and is 

 found also in the coffee-bean, the Vaccinium myrtillus, and 

 other plants. It is closely allied to benzoic acid, and appears 

 in the urine as hippuric acid. See Benzoinum, page 281. 



b. Kinovic _acid^ C^H^gO^, " kinova bitter," is a white 

 amorphous body, insoluble in water. It appears to be a 

 product, with glucose, of kinovin, a glucoside. 



c. Cincho-tannic acid, the astringent principle and soluble 

 red-colouring matter of the bark, amounts to 1 to 3 per cent. 

 It is a yellow hygroscopic body, and differs from ordinary 

 tannic acid in striking green with persalts of iron, and in being 

 very readily oxydised, one of the products being 



4. Cinchona red, a reddish-brown substance without taste 

 or smell, nearly insoluble in water. 



5. The volatile oil, obtained by distillation, has the odour 

 of the bark. 



Impurities. Inferior barks are detected by the absence of 

 the true characters of the officinal barks, and by a quantitative 

 test. This consists in (1) boiling 100 gr. of the bark in water 

 acidulated with' HC1, macerating, and percolating ; (2) precipi- 

 tating the colouring matter with solution of subacetate of lead ; 

 (3) adding caustic potash to the filtrate, until the precipitate 

 first formed is nearly redissolved ; (4) agitating with ether, and 

 evaporating the resulting solution. This should yield not less 

 than 2 gr. of quinia from yellow bark ; 2 gr. of alkaloids from 

 red bark ; and gr. of alkaloids from pale bark. The 

 yellow bark is adulterated with elm, larch, and Winter's barks, 

 known by absence of bitter taste ; the pale bark with 

 cascarilla, which is whiter ; the red bark with red sandal wood, 

 logwood, and larch barks, which are all devoid of a bitter 

 taste. 



Incompatibles. Ammonia, lime-water, metallic salts, and 

 gelatine. May be combined with mineral acids. 



Dose of any of the barks. 15 gr. as a tonic; 1 to 2 dr. in 

 ague. 



Preparations. 



A. Of the Tellow Bark : 



1. Decoctum Cinchona Flavse. 1 in 16. Dose, 1 to 2 fl.oz. 

 'L gxtractum Cinchona FlavsB Liquidum. 4 in 1. Dose, 10 

 to 30 min. 



