62 SUBSTANCES SOLUBLE IN ALCOHOL. 



Berberine. 1 cc. indicates 0*0425 gram berberine (Beach). 1 

 The precipitate is stated to contain almost exactly half its weight 

 of pure berberine. 



Quinine. According to Prescott 2 the double salt of quinine 

 with iodide of mercury contains 34 '5 per cent, of alkaloid, and is. 

 almost insoluble in water. From the recent researches of Hielbig a 

 it would appear that no special advantage is to be looked for in 

 the application of potassio-mercuric iodide to the quantitative 

 estimation of quinine. 



Chelidonine and Sanguinarine. From some experiments made by 

 Masing I anticipate that 1 cc. of potassio.-mercuric iodide will be 

 found to indicate '01 6 75 gram of the former and '01 48 5 gram 

 of the latter. 4 (Compare also 174 et seq.) 



66. Estimation ofTheine, etc. The quantitative determination 

 of some alkaloids may be made as follows : The material is boiled 

 with water, either pure or containing a little sulphuric acid, the 

 filtered or strained decoction evaporated with magnesia or lime, 5 

 and the residue finely powdered with sand or some other inert 

 substance. It is then extracted with ether, chloroform, or other 

 suitable solvent, the filtered solution evaporated and the residue 

 weighed. 6 I have found this method well adapted for estimating 

 the alkaloid in tea (without the addition of acid). 



Similar methods have also been proposed for the estimation of 

 the total alkaloid in cinchona-bark, but the long-continued action 

 of the dilute acid necessary to dissolve the alkaloid appears to 

 decompose part of it and renders the estimation inaccurate. (Com- 

 pare 176.) 



67. Extraction of Cinchona Alkaloids. In a series of experi- 

 ments in my laboratory the following method was found by 

 Hielbig 7 to be the most advantageous : 25 grams of powdered 

 bark are digested with 100 grams of 1 per cent, sulphuric acid at the 

 ordinary temperature for twenty-four hours, care being taken to ex- 



1 American Journ. Pharm. xlviii. 386. 



2 Ibid. xlix. 482. 



3 Kritische Beurtheilung, etc. Diss. Dorpat. 



4 Compare my Chemische Werthbestimmung, p. 101. Also Naschold, 

 Journal f. prakt. Chem. cvi. 385. 



6 Compare Cazeneuve, Jahresb. f. Pharm. 1875, 342. 



6 Compare also Losch, Pharm. Zeitschr. f. Russland, xviii. 545,-and my re- 

 marks on his method, Jahresb. f. Pharm. 1879, 165 (Year-book Pharm. 

 1880, 60). . 



7 Loc. cit. 



