§ 187. ESTIMATION OF MORPHINE. 199 



isolated in the examination of the bark. It may be separated as 

 follows : The mixed alkaloids are dissolved in dilute acetic acid, 

 and to the solution sulphocyanide of potassium is added until the 

 colour is only pale yellow. After standing till perfectly clear it 

 is filtered, the filtrate made alkaline with ammonia and shaken 

 with ether. The residue obtained by evaporating the ethereal 

 solution is then recrystallized from alcohol. Quinamine dissolves 

 in 32 parts of ether, and is also soluble in boiling petroleum 

 spirit. The precipitate produced with chloride of gold rapidly 

 decomposes with production of a red colouration. 



For paricine, see § 181 ; paytine, §§ 183, 189. Hesse states 

 of the latter that it is coloured purplish-red by chloride of gold, 

 and red passing to blue by chlorinated lime. 



For other cinchona alkaloids, see Hesse in the jjapers, etc., 

 already quoted.^ 



§ 187. Estimation of Opitmi. — Many methods have already been 

 proposed for the estimation of the more important opium alkaloids. 

 I have criticized them at length in my ' Chemische Werthbestim- 

 mung,' and restrict myself, therefore, here to recapitulating the 

 modification of the Guibourt-Schacht's process there recommended, 

 adding a few remarks on methods that have appeared since the 

 publication of that work. 



I. Five to ten grams of powdered opium are triturated with 

 water to a very thin paste, macerated twenty-four hours and 

 filtered. The residue is again treated in the same manner, and 

 finally washed on the filter until the washings are colourless. 

 When dried the insoluble portion should not amount to more 

 than 40 per cent, of the opium employed. It still contains nar- 

 cotine, which may be estimated according to VI. 



II. The aqueous infusions and washings are evaporated in the 

 water-bath until reduced to about five times the weight of the 

 opium employed, cooled, filtered if necessary, and mixed with the 

 slightest possible excess of ammonia. ^ It is then vigorously stirred, 



1 Compare also Ber. d. d. chem. Ges. xi. 1938, 1878 (Pharm. Journ. and 

 Trans. [3], xi. 839, 1881) ; Annal. d. Chem. und Pharm, ccv. 194, 211, 1880 

 (Year-book Pharm. 24, 27, 28, 1879 ; 42-44, 1881). 



2 See Cleaver, Amer. Journ. Pharm, xlviii. 359, 1876 (Pharm. Journ. and 

 Trans. [3], vii. 240), and my remarks in the Jahresb. f. Pharm. 175, 1876. 

 Cleaver, who also employs a modification of Mohr's process, recommends the 

 opium to be previously exhausted with bisulphide of carbon, which removes 

 substances that interfere with the subsequent operations. 



