§ 192. SEPARATION BY SOLVENTS. 191 



Carbonated alkalies may occasionally Ije used instead of caustic. 

 For the separation of some alkaloids bicarbonates have also been 

 recommended, as it was found that under certain conditions one 

 alkaloid would form a soluble carbonate, whilst the other was 

 immediately precijiitated in the free state. In this way paricine can 

 be separated from the other bark alkaloids by bicarbonate of soda. 



§ 182. Behaviour to solvents. — Separation may be accomplished in 

 this way, either by treating the dry alkaloids with the solvent, or 

 by shaking it with the liquid containing the alkaloids in solution. 



An instance of the first case may be found in the separation of 

 brucine and strychnine from a mixture of the two alkaloids pre- 

 cipitated by ammonia. Absolute alcohol dissolves brucine with 

 tolerable facility, but takes up only a minute proportion of strych- 

 nine.^ Another method, Avhich I form^erly employed for the 

 separation of these two alkaloids, may also find a jDlace here. It 

 consisted in allowing the benzene solution of the mixed alkaloids 

 to evaporate until the majority of the strychnine had separated, 

 then quickly jDouring off" the mother liquor, washing Avith benzene, 

 and evaporating to dryness ; the brucine was thus obtained, mixed 

 with a little strychnine (0"0683 gr. for every cc). I have suc- 

 ceeded in separating the two alkaloids tolerably completely by 

 both of these methods, but as they occasionally fail I cannot 

 further recommend either of them ; the first is, however, the 

 more preferable of the two. 



By treatment with water colchicine may be separated from the 

 colchiceine, which sometimes accompanies it in Colchicum corms. 

 The quantity of solvent used must not, hoAvever, be too small, as 

 colchiceine is more soluble in concentrated aqueous solutions of 

 colchicine than in pure Avater, Avhicli dissolves it but very 

 sparingly.- 



Moens,^ Stoeder,^ and Hielbig,'' found 40 per cent, spirit 

 adapted for the separation of the cinchonine and ' amoi'jphous 



^ Compare my ' Werthbestimmiing,' 66. Even if the greater part of the 

 free ammonia present be allowed to evaporate, the complete precipitation of 

 brucine is a matter of difficulty ; that portion of the alkaloid that remains in 

 solution must therefore be removed by shaking with benzene. 



2 See Hertel, Pharm. Zeitschr. f. Russland, Nos. 13 to 18, 1881 (Pharm. 

 Journ. and Trans. [3], xii. 498). 



3 Nieuw Tijdschrift voor de Pharm, in Nederl,, 322, 1869 ; 7, 1870 ; 161, 

 1875. 



* Archiv d. Pharm. [3], xiii. 243, 1878 (Journ. Chem. Soc. xxxvi. 281). 

 ■'' Kritische Benrth. der Method, zur Trennung und quant. Best. d. China- 

 alkaloide,' Diss. Dorjjat, 1880. 



