REMARKS UPON THE METHODS 169 



composed or otherwise altered that the investigator should 

 seelj to isolate them by the simplest methods possible. If 

 it can be done without the addition of any acid or without 

 tlie application of heat, so much the better. 



Especially is the modification of this method employed 

 by Mareno-Zuco, and already described, to be commended. 



By his method, Brieger has discovered a considerable 

 number of basic bodies and has given great impetus to the 

 study of the chemistry of putrefaction. The method is 

 capable of a great many modifications. As long ago as 1868, 

 Bergmann and Sohmiedkbbrg employed precipitation 

 with metallic salts in order to obtain sepsine from putrid 

 yeast. The method used by them was as follows : Putrid 

 yeast was diffused through parchment paper; the diffusate 

 was acidified with hydrociiloric acid, and treated with mer- 

 curic chloride solution until a heavy cloudiness and, after 

 some time, a slight precipitate formed. This was removed 

 by filtration ; the filtrate was rendered strongly alkaline 

 with sodium carbonate, and then further treated with a 

 solution of mercuric chloride as long as a precipitate 

 formed. This precipitate was collected on a filter, washed, 

 suspended in a little acidified water, and decomposed with 

 hydrogen sulphide. The precipitate was removed, the free 

 hydrochloric acid in the filtrate taken up with silver car- 

 bonate, and the excess of silver removed with hydrogen 

 sulphide. The filtrate was evaporated to dryness; the 

 residue dissolved in alcohol (a part remaining insoluble), 

 and acidified with sulphuric acid, when a colorless or 

 slightly yellow crystalline precipitate formed. The crys- 

 talline sepsine sulphate was purified by solution in water 

 and precipitation with alcohol. 



Brieger has obtained some of his bases by a much sim- 

 plified modification of his complete method, which we have 

 given in full. For instance, in obtaining neuridine, he 

 treated the aqueous extract of the putrid material, after 

 boiling and filtration, with mercuric chloride, collected the 

 precipitate, decomposed it with hydrogen sulphide, evapor- 

 ated the filtrate on the water-bath, and extracted the base 

 from the residue with dilute alcohol. 



