CHAPTEE VIII. 



METHODS OF EXTRACTING PTOMAINES. 



Feom what has beeu given in the preceding pages, one 

 may gather some idea of the peculiar difficulties with which 

 the chemist has to contend in his endeavors to isolate the 

 basic products of putrefaction. He has to deal with very 

 complex substances, of the nature and reactions of many 

 of which he must be ignorant. Besides, the substances 

 which he seeks are often most prone to undergo decompo- 

 sition, and in this way escape detection. Many ptomaines 

 are volatile or decomposable at any temperature near that 

 of boiling water. In these cases, solutions cannot be 

 evaporated in the ordinary way and the poison separated 

 from the residue. Indeed, the investigator has frequently 

 been disappointed when on the evaporation of a solution, 

 which he has demonstrated to be poisonous, he finds that 

 the residue is wholly inert. Again, he may destroy the 

 ptomaine by the action of reagents which he uses. So 

 simple a procedure as the removal of a metallic base from 

 a solution containing a ptomaine, by precipitation with 

 hydrogen sulphide gas, has beeu known to destroy wholly 

 the ptomaine. Probably the most perplexing difficulty in 

 the isolation of these putrefactive alkaloids lies in the great 

 number, complexity, and diversity of the other substances 

 present in the decomposing mass. The same ptomaine may 

 be present in pqual quantities in two samples of milk, and 

 yet it may be easily obtained from the one, while from the 

 other only minute traces can be secured. The difference is 

 due to the fact that the other constituents of the milk in 

 the two samples are at different stages of the putrefactive 

 process, and, consequently, differ greatly in their reactions 

 and in their effects upon the agents employed to isolate 

 the poison. All chemists will appreciate these difficulties. 



8 



