TESTS FOR CINCHONA BARKS 
43 
to twenty-four hours at the same temperature with 8 to 9 oz. of 
water and a few drops of dilute sulphuric acid until the last filtrate 
was rendered but faintly turbid by ammonia. The whole of the 
extracts were united, and the alkaloid precipitated until a filtered 
sample was no longer rendered turbid by ammonia. The precipi- 
tated quinine was collected upon a filter, washed, pressed, and 
dried. In the moist state it had a chocolate-brown color ; when 
dry, it was dark reddish brown, and weighed 21 grs. There were 
therefore 2-187 per cent, of colored quinine ; the time requisite for 
this process may be further shortened by boiling, instead of di- 
gesting at the above mentioned temperature. 1 oz. of the powder- 
ed bark was boiled half an hour with 12 oz. of water and \ a 
scruple of dilute sulphuric acid, and the residual powder washed 
out with about 4 oz. more hot water, and the filtered solution im- 
mediately precipitated with ammonia or carbonate of soda. The 
precipitate is washed with cold water, and dried between blotting 
paper. 
The author purified this colored quinine. This operation, how- 
ever, was accompanied by so great a loss, that, calculating the 
quantity in the bark from the quantity of pure quinine obtained, 
it would amount only to J per cent. For the purpose of testing 
a bark as to its genuineness, it suffices merely to prepare the 
colored quinine, and this method is then both quick and simple. 
This method was applicable to the examination of the barks of 
Cinchona fusca, C. Huamalies, C.Jlava, and C. Surinamensis. 
C. Brasiliensis. The test is easily applied and decisive when the 
question to decide is whether the powder has been prepared from 
C. regia, C. fusca, or C.Jlava, or from any false Cinchona barks. 
Yellow bark, exhausted with hot water to which a little sulphuric 
acid has been added, furnishes a pale yellow infusion of a peculiar 
aromatic odor, which, on being mixed with an excess of ammonia, 
gives a copious reddish-brown precipitate, and the liquid at the 
same time assumes a beautiful red color ; red bark, on the other 
hand, furnishes a brownish-yellow or ochreous precipitate, and 
the infusion is colored yellowish-brown by the ammonia. The 
pale Carthagena bark likewise yields with water acidulated with 
sulphuric acid a pale sherry-colored infusion, which also gives a 
chocolate-brown precipitate with ammonia, like the infusion of 
yellow bark ; but the filtered ammoniacal liquid is not red, but 
