46 PHYSIOLOGICAL AND PATHOLOGICAL CHEMISTRY 



Preparation of Peptone. 



The solution obtained in the precipitation of the albu- 

 moses contains peptone together with traces of albumoses, 

 especially deuteroalbumose. Dissolve, by heating, 20 g. more 

 of ammonium sulphate in this solution, or so much of it as 

 may be necessary to form a saturated solution, and make 

 alkaline with ammonia and ammonium carbonate. After 

 cooling, filter, heat until the odor of ammonia has disappeared, 

 saturate again at the boiling-point with ammonium sulphate, 

 let cool, and when perfectly cold filter from the ammonium 

 sulphate and traces of albumose which separate. 1 Before 

 preparing peptone from the filtrate determine by the biuret 

 reaction whether it contains any considerable quantity of 

 peptone. For this purpose add to a portion of the filtrate 

 so much caustic soda solution of 1.34 specific gravity that 

 sodium sulphate begins to separate, then add the copper 

 sulphate solution. If an intensely red fluid does not result, 

 further work with the solution will not pay. The removal 

 of ammonium sulphate from the solution is accomplished in 

 the same manner as with albumose, by boiling with barium 

 carbonate, etc. It is advisable, however, before treating 

 with barium carbonate to separate a part of the ammonium 

 sulphate by evaporation and crystallization and also by pre- 

 cipitation with alcohol, in which the peptone dissolves. Since 

 the barium carbonate as a rule is not entirely free from solu- 

 ble salts, these together with the sodium chloride accumulate 

 in the fluid containing the peptone, so that the peptone 

 obtained always yields considerable ash. 



The reactions are the same as those of albumose but no 



1 To effect a complete separation, the solution made acid with acetic 

 acid must be again saturated with ammonium sulphate at the boiling- 

 point, allowed to cool, and filtered once more. Kuhne, Zeitschr. f. Biol. 

 29, 1 (1892). O. 



