4 1 2 CHEMISTR Y OF THE DIGESTIVE PROCESSES. 



The amphopeptone is obtained from the filtrate after removal of the 

 ammonium sulphate by complicated methods, consisting essentially in the 

 removal of ammonium sulphate as far as possible by concentration ; solution 

 of the amphopeptone in weak alcohol; removal of as much ammonium 

 sulphate from the weak alcohol as possible by a freezing mixture ; removal of 

 the alcohol by distillation ; removal of the last portions of ammonium sulphate 

 by boiling with barium carbonate ; removal of the last traces of barium salts by 

 cautious addition of dilute sulphuric acid ; and finally, precipitation of the 

 amphopeptone by excess of absolute alcohol. 



Neumeisters method for separating the albumoses of peptic, digestion. 

 The method of Kiihne and Chittenden for the separation of the 

 various albumoses has been perfected by Neuineister, 1 who has in 

 addition proved that these bodies are not formed synchronously in the 

 process of digestion, or other form of 'hydrolysis, but that there are two 

 stages in the process. In the first stage proto- and /^eroalbumoses are 

 formed, which are called for this reason primary albumoses ; in the second 

 stage each of these primary albumoses gives rise to a deuteroalbumose, 

 and these deuteroalbumoses are hence called secondary albumqses. 



Since heteroalbumose is completely and protoalbumose only partially 

 precipitated by saturation with sodium chloride in neutral solution, 

 while deuteroalbumose is not precipitated at all, it is easy, from a 

 mixture of all three albumoses, to obtain a solution containing only 

 heteroalbumose and protoalbumose ; and on dialysis of this solution 

 heteroalbumose, being insoluble in water, is precipitated alone, leaving 

 in solution only pure protoalbumose. In this way pure proto- and 

 heteroalbumoses can be obtained, but the preparation of pure deutero- 

 albumose is not quite so easy. In the filtrate from saturation with 

 sodium chloride there is not only deuteroalbumose but the unprecipitated 

 residue of the protoalbumose, and on adding acetic acid this is thrown 

 out along with the deuteroalbumose. However, a loophole is left in the 

 fact that just as saturation in neutral solution does not precipitate all 

 the protoalbumose, so saturation in acid solution does not precipitate all 

 the deuteroalbumose. Neuineister took advantage of this, sacrificed 

 the first portion of deuteroalbumose thrown out by the acetic acid, 

 accompanied by the last portions of protoalbumose, and then precipitated 

 the fraction of deuteroalbumose left alone in solution by saturation with 

 ammonium sulphate. 



Kiihne and Chittenden had already got round this difficulty of isolating 

 deuteroalbumose by treating a dried mixture of the albumoses, such as is found 

 in Witte's peptone, with neutral and saturated solution of sodium chloride. 

 Here the deuteroalbumose only passes into solution. Although the proto- 

 albumose would only be partially thrown out of solution by saturating with 

 sodium chloride, yet it has not the power when dry to pass into solution 

 in such a solvent. Witte's peptone is, however, a variable mixture, and 

 Neumeister, working with other samples, was unable to reobtain Kiihne and 

 Chittenden's result ; it may be that they were working with a sample 

 containing little or no protoalbumose. 



Neumeister effects the separation as follows : 



The faintly acid solution is saturated with ammonium sulphate, and so 

 separated from peptones. The precipitate is dissolved by the addition of 

 water, separated from the excess of the salt by dialysis, and then the neutral 



1 Ztschr.f. Biol., Miinchen, 1887, Bd. xxiii. S. 381 ; ibid., 1888, Bd. xxiv. S. 267 ; ibid., 

 1890, Bd. xxvi. S. 324. 



