174 CHEMISTRY OF THE PROTEIDS CHAP. 



Albumoses are again subdivided into primary and secondary 

 albumoses. The primary may greatly resemble the albumins ; they 

 are precipitated, and thus separated from the secondary albumoses, 

 by either completely saturating their solutions with sodium chloride, 

 or half saturating them with ammonium sulphate. The primary 

 albumoses are represented by the proto- and the hetero-albumose. 

 Kiihne also describes a dys-albumose, but it is now generally believed 

 that the latter represents hetero-albumose which has become insoluble. 

 The secondary or deutero- albumoses are in many instances only 

 divided from the peptones by arbitrary definitions. 



Beyond the stage of peptones we come to the peptids or sub- 

 stances built up of two or more amino-acids on exactly the same 

 principles as are albumins, and which therefore, from the chemical 

 standpoint, are doubtless albumins. A number of di- and poly-peptids 

 have been prepared synthetically by Curtius and Fischer and their 

 pupils, as stated in Chapter III. It is difficult to separate peptids 

 from peptones ; the most ready, but again arbitrary, method would be 

 to make use of the biuret-reaction ; thus peptones do, while peptids 

 do not, give this reaction. The peptids are called by Hof meister l 

 peptoids. 



Albumoses, when in the dry state, are white, dust -like, non- 

 crystalline powders. With the exception of the hetero -albumoses, 

 they are readily soluble in water ; still more soluble are many of their 

 salts. They are all precipitable by alcohol, the different albumoses 

 being precipitated by different concentrations of alcohol. Albumoses 

 give a red biuret-reaction with a tinge of violet. All albumoses give 

 the xanthoproteic test, while the other colour tests are either negative 

 or positive according to the radicals contained in the individual 

 albumoses, 



Albumoses show, according to Kiihne, 2 Neumeister, 3 and Hof- 

 meister's school, 4 the following precipitation tests : Albumoses are 

 precipitated by ferric chloride, neutral and basic lead acetate, mercuric 

 chloride, platinum chloride, and other metallic salts, but the precipitates' 

 are more or less soluble in an excess of the precipitating agent. 

 Copper sulphate, and the even more sensitive copper acetate, precipi- 

 tate only the primary but not the deutero-albumoses, and are therefore 

 used to separate the primary from the secondary albumoses. 



1 F. Hofmeister, Ergebnisse der Physiologic v. Asher-Spiro, I. 1. 759 (1902). 



2 W. Kiihne and R. H. Chittenden, Zeitschr. f. Biol. 20. 11 (1884). 



3 K. Neumeister, ' tJber die Reaktionen der Albumosen uud Peptone,' ibid. 26. 

 324 (1890). 



4 E. P. Pick,. Zeitschr'. f. .physiol. Ohem. 24. 246 (1897); E. Zunz, ibid. 27. 219 

 (1899). 



