THE STAS-OTTO METHOD. 231 



Guareschi and Mosso found commercial alcohol almost invariably 

 to contain small quantities of an alkaloidal substance, the odor of 

 which is similar to that of nicotin and pyridin. Its solutions are 

 precipitated by the general alkaloidal reagents, with the exception 

 of platinum chlorid and tannic acid. It does not reduce, or reduces 

 feebly, ferric salts. From one sample of alcohol they obtained a 

 base which, on addition to the above reagents', did give a precipitate 

 with platinum chlorid. Alcohol may be freed from these substeinces 

 by distillation over tartaric acid. 



In amylic alcohol, Haitinger found almost 0.5 per cent, of pyridin. 

 This reagent may be purified in the manner recommended for 

 ethylic alcohol. 



Chloroform, when found to leave a residue on evaporation, should 

 be washed first with distilled water, then with distilled water ren- 

 dered alkaline with potassium carbonate, then dried over calcium 

 chlorid and distilled. 



Petroleum ether sometimes contains a base which has an odor 

 similar to trimethylamin or pyridin, and which gives a precipitate 

 with platinum chlorid, forming in octahedra ; benzol may contain a 

 similar substance. 



The following methods have been used for the purpose of extract- 

 ing putrefactive alkaloids : 



The Stas-Otto Method. — This method depends upon the follow- 

 ing facts : (1) The salts of the alkaloids are soluble in water and 

 alcohol, and generally insoluble in ether, and (2) the free alkaloids 

 are soluble in ether, and are removed from alkaline fluids by agita- 

 tion with ether. These principles are capable of great variations in 

 their application. The usual directions are as follows : Treat the 

 mass under examination with about twice its weight of 90 per cent, 

 alcohol, and from ten to thirty grains of tartaric or oxalic acid ; digest 

 the whole for some time at about 70°, and filter. Evaporate the 

 filtrate at a temperature not exceeding 35° either in a strong current 

 of air or in vacuo over sulphuric acid. Take up the residue with 

 absolute alcohol, filter, and again evaporate at a low temperature. 

 Dissolve this residue in water, render alkaUne with sodium carbon- 

 ate, and agitate with ether. After separation remove the ether with 

 a pipette, or by means of a separator, and allow it to evaporate spon- 

 taneously. The residue may be further purified by redissolving in 

 water, and again extracting with ether. 



The following modifications of this method are employed : 



Instead of tartaric or oxalic acid, acetic acid may be used. 



When the fluid suspected of containing a ptomain is already acid 

 from the development of lactic or other organic acid, the addition of 

 an acid may be dispensed with. 



Ether extracts are made from both acid and alkaline solutions. 



