292 VETEEINAEY TOXICOLOGY 



On the basis of these facts, an extraction of the acid 

 liquid will yield glucosides, bitter principles, acid, and 

 neutral compounds, and a subsequent extraction of the 

 liquid made alkaline by ammonia will yield alkaloids. The , 

 two groups are thus partially separated, but many alka- 

 loids are extracted from acid solution (being feeble bases) — 

 e.g., chelidonine, veratrine, colchicine, and solanidine. 



The solvent to be used depends on the nature of the 

 dissolved substance which it is desired to extract. Of those 

 named petroleum ether has the most limited range, and 

 amyl alcohol the widest. Attempts have been made to 

 separate the possible components by systematic extraction. 

 Thus Dragendorff developed a complete scheme depen- 

 dent on — 



(a) Successive extraction of the acid liquid with petroleum 

 ether, benzene, chloroform, and amyl alcohol. 



(b) Extraction by the same solvents in the same order of 

 the liquid made alkaline by sodium hydroxide. 



(c) Extraction by amyl alcohol after replacing sodium 

 hydroxide by ammonia (by saturating with ammonium 

 chloride) for morphine. 



(d) The residual solution contains non-extractible com- 

 pounds — curarine. 



This scheme has little or no value in practice, partly 

 because it rarely happens that more than one or two 

 poisons are present, but chiefly because the separation is not 

 sharp. Many compounds pass into each of the solvents in 

 variable proportion, and are thus spread out over several 

 fractions. 



In actual experience, successive extractions with ether 

 and chloroform (a) from acid and (b) from ammoniacal solu- 

 tion are sufficient. Instead of chloroform, it is very con- 

 venient to use ethyl acetate, which possesses nearly as wide 

 a range of solvent power, which separates more easily from 

 emulsion than chloroform, and which forms a layer lighter 

 — and not like chloroform, heavier — than water. 



The various extracts are evaporated either spontaneously 

 or at a gentle heat in porcelain dishes, or on a porcelain 



