302 PROTEINS 



such as aluminium, chromium, zinc, lead, tin, manganese, 

 arsenic or antimony, all of which are weak bases or acids. 



The fact that egg albumen is able to neutralize hydro- 

 chloric acid was first observed by Sjoqvist,* and later by 

 Bugarsky and Liebermann ; f moreover, the fact that both 

 basic dyes such as rosanilines, as well as acid dyes such as 

 picric acid, are able to combine with wool fibres, points to 

 the amphoteric nature of the protein in this case also. 



The simultaneous possession by a body of both acidic and 

 basic groupings J is well illustrated by the amino acids ; the 

 true amphoteric character is, however, only illustrated by those 

 of them that are sufficiently weak acids, or whose acidic and 

 basic functions are about equally strong. 



The observation that the hydrochloride of albumen is pre- 

 cipitated by the addition of sodium phosphomolybdate, whereas 

 albumen itself is not, led Spiro and Pemsel § to conclude that 

 albumen belongs to a class of compounds which, although 

 electrically charged, are not ionized, and while not functioning 

 as acids or bases themselves, are none the less able to form 

 addition compounds with such substances. According to 

 Sjoqvist II and Bugarsky and Liebermann,1F albumen forms 

 with acids and bases true salts, which obey all the laws of 

 Van't Hoff and Arrhenius, though, on the other hand, its 

 low conductivity would appear to preclude the possibility of 

 its possessing well-marked hydrogen or hydroxyl ions. These 

 facts are, however, readily explained by assuming proteins to 

 be pseudo-bases of the type described by Hantzsch ** and his 

 collaborators. Hantzsch describes as pseudo-bases a class of 

 compounds which are chemically indifferent, but which on 

 coming in contact with acids undergo molecular rearrange- 

 ment, giving rise to true bases. 



This change, which may be represented as follows, 

 N = ROH-^R = N-OH 

 implies a change from a neutral carbinol to a true ammonium 



* Sjoqvist: " Skand. Arch. Physiol.," 1895, 5, 354. 



+ Bugarsky and Liebermann : Pfliiger's " Archiv Physiol.," 1898, 72, 68. 



JWinkelblech : "Zeit. physikal Chem.," igoi, 36, 551. 



§ Spiro and Pemsel: " Zeit. physiol. Chem.," 1898, 26, 270. 



Il Sjoqvist: "Skand. Arch. Physiol," 1895, 5, 277. 



IT Bugarsky and Liebermann: "Zeit. gesam. Physiol.," 1898, 72, 68. 



** Hantzsch : " Ber. deut. chem. Geselis.," 1899, 32, 575, 3109 ; 1900, 33, 278. 



