CHEMICAL COMPOSITION OF THE HUMAN BODY 37 



The proteoses give all the proteid color reactions, but not all 

 the precipitation reactions. 



The proteoses behave towards the mineral acids and bases 

 like amido acids ; the acids are simply added to the ammonia 

 group, and the metals of the bases replace the hydrogen of 

 the carboxyl groups. 



Proteoses, like native proteids, are neutral because the acid 

 carboxyl and the basic ammonium nucleus are both neutralized by 

 their intimate union. Mineral acids destroy this union, the strong 

 acid replacing the carboxyl, hence the compound formed is acid 

 because of the free carboxyl groups. If proteoses combine with 

 alkali, the ammonium group is set free and the compound formed 

 has an alkaline reaction. The power of proteoses to combine 

 with acids and alkalies is the greater the further the splitting up 

 of the proteid has been carried ; it is greatest in peptone in which 

 the combining power is many times that of the native proteid. 



The albumoses differ from the peptones not only in the 

 size of the molecule and the percentage of suphur, but also 

 in the precipitation by salts. Albumoses are precipitated by 

 saturating their solution with ammonium sulphate; peptones 

 are not thus precipitated. 



Albumoses are divided into primary and secondary albu- 

 moses which differ from each other in their solubility. The 

 primary albumoses (protalbumose and heteroalbumose) are 

 precipitated from a neutral solution by saturating with NaCl. 

 The secondary albumoses (deuteroalbumose) are thus pre- 

 cipitated only from acid solutions ; sometimes they are not 

 precipitated by NaCl at all. 



The secondary albumoses are with greater difficulty precipitated 

 by other reagents also; they are not precipitated by nitric acid or 

 2% copper sulphate solutions, and their precipitation by potassium 

 ferrocyanide and acetic acid is slow and incomplete. The primary 

 albumoses obtained from the crystallized serum albumin contain 

 more firmly combined sulphur, the secondary has more loosely 

 combined sulphur. 



Judging from the freezing-point, it is supposed that deutero- 

 albumose has a larger molecular weight than protalbumose. 

 Hence the deuteroalbumoses cannot be regarded as the splitting- 

 up products of protalbumoses. 



Peptones are not precipitated by any proteid precipitant 



