184 ALKALOIDS. 



brucine salt from ?/ = 7-1733 (m-'0-01852 x f), c being the same 

 as in the pre\'ious expressions and m denoting the weight of the 

 mixed hydrochlorates. 



Titration of morpliine and narcot'me with potassio-niercuric iodide 

 serves only as a check on the weight of the alkaloids after 

 isolation (§§ 182, 187). The total alkaloid in opium cannot be 

 estimated volumetrically with that reagent. 



For a method of examining chdidoniuni compare § 65 and my 

 ' Werthbestimmung,' p. 98. 



The presence in cevadilla seeds of three alkaloids, all of which 

 act upon potassio-mercuric iodide, renders it impossible to do more 

 with this reagent than compare the extracts of two or more 

 different samples of seeds wath one another.^ If an approximate 

 separation of the three alkaloids is desired, it must be remembered 

 that, according to the investigations of Weigelin,- all three are re- 

 moved together by shaking Avith chloroform ; that sabadilline is 

 almost insoluble in ether, but is dissolved by 150 parts of Avater at 

 the ordinary temperature ; that sabatrine is freely soluble in ether 

 and soluble in 40 parts of cold Avater; and finally that veratrine is 

 said to be taken up by 10 jiarts of ether and 1,000 of cold Avater. 



The researches of Harnack and WitkoAvski have proved^ 

 that the calabar lean also contains tAvo alkaloids (calabarine and 

 physostigmine), differing from one another in physiological action. 

 For this reason the estimation of the total alkaloid by titration 

 Avith potassio-mercuric iodide has only a limited value, but the 

 alkaloids might possibly be separated, and estimated gravimctri- 

 cally, as the calabarine precipitate is insoluble in alcohol Avhilst that 

 produced by physostigmine is soluble. 



^' 175. Coniine, jjilocarjpine, etc. — Zinoffsky has shoAvn that 

 coniine can be accurately estimated by phosphomolybdic acid in 

 solutions free from ammoniacal salts.'* The strength of the 

 reagent was such that 1 cc. precipitated 05 gram of coniine. 



1 Compare E. Masing, Archived. Pharm. [3], ix. 310, 1876 ( Joiirn. Chem. 

 Soc. xxxii. 367). 



- Compare Weigelin, 'Unters, liber die Alkaloide der Pabadillsamen,' Di.ss. 

 Dorpat, 1871 (.Journ. Chem. See. xxv. 828). See also P. G. A. Masing, 

 ' Beitr. z. gerichtl. chem. Nachw. des Strychn ins n. Veratrins,' Diss. Dorpat, 

 1868. 



=* Compare Archiv f. exper. Patholog. und Pharnuicol, v. 401, 1876 (Pharm. 

 Journ. and Trans. [3], viii. 3). 



■* ' Die ([iiant. Best. d. Emetins, Aconitins und Nicotins,' Diss. Dorjjat, 

 1872 (Pharm. Journ. and Trans. [3J, iv. 442). 



