42 PHYSIOLOGICAL AND PATHOLOGICAL CHEMISTRY. 



dish with sodium carbonate solution, and filter from the pre- 

 cipitate formed. Show that the precipitate consists essen- 

 tially of acid albumin (solubility in dilute alkalies, precipita- 

 tion by mineral acids) . The filtrate is evaporated, at first by 

 heating it to boiling over a free flame. Some proteid, appar- 

 ently globulin, always precipitates at this point. This is 

 filtered off before the solution has been much concentrated. 

 During the evaporation the reaction must be kept as nearly 

 neutral as possible (by means of sodium carbonate or dilute 

 hydrochloric acid). Evaporate on the water-bath to about 

 200 cc. 1 It is now necessary to separate the albumoses from 

 the peptone. This may be done by saturating the solution, 

 acidified with acetic acid, with sodium chloride, or by com- 

 pletely saturating it with ammonium sulphate. The albu- 

 moses are precipitated, while peptone remains in solution. 

 The advantage of ammonium sulphate over acetic acid and 

 salt lies in the more complete precipitation of the albumoses; 

 however, even when ammonium sulphate is used some 

 deuteroalbumose (Kiihne) frequently remains unprecipitated ; 

 the disadvantage consists in the fact that the removal of the 

 ammonium sulphate afterwards offers far greater difficulties 

 than that of the sodium chloride. 



Separation of the Albumoses from Peptone by Means of 

 Ammonium Sulphate. 



Put the solution evaporated to 200 cc. into a large mortar 

 containing 100 g. of finely ground ammonium sulphate. 

 Grind thoroughly until the ammonium sulphate is all dis- 

 solved and separate the viscous mass of albumoses, which 

 precipitates, from the solution by decantation. The solution 

 is kept; the precipitate is ground once more with a solution 



1 By precipitating a solution of this kind with alcohol the commercial 

 peptone (mixture of albumoses and peptone) is prepared. 



