vii HALOGEN-ALBUMINS 237 



substitution products. When nitrating albumins, the sulphur is also 

 oxidised, and therefore no lead sulphide reaction is obtained, although 

 both xanthoprotein and the nitro-albumoses retain the whole of their 

 sulphur. The reaction of Millon gives negative results, because the 

 nitration takes place in the tyrosin group. 1 In other respects the 

 iiitro-substitution products give the usual proteid-reactions. 



Xanthoprotein on being dissociated with acids yields leucin, 

 glutaminic and aspartic acids, and the nitro-substitution product xantho- 

 melanin (see p. 95), derived from the original tyrosin. By peptic 

 and tryptic digestion are liberated nitrated albumoses and peptones. 



Physiologically, xanthoprotein is not indifferent, because 50 g. 

 administered to a dog by the mouth produce symptoms of poisoning, 

 which apparently are due to the xanthoprotein as a whole and not 

 simply due to the nitro-groups. In the urine, xanthomelanin, or an 

 allied body, is found. 



Oxyproteic Acid or Oxyprot-sulphonic Acid 



B6champ 3 was the first to study the effect of potassium permanganate 

 on albuminous substances, and to point out that oxidation gives rise 

 to urea. This statement, after a great deal of controversy, has been 

 now definitely settled by Kutscher and Zickgraf. 2 Be"champ 3 was 

 followed by Subbotin 4 and Pott, 5 of whom the latter isolated from the 

 conglutin of lupines an acid having the following percentage com- 

 positions : 



C H N 



45.44.45-53 5-84-5-88 13-06-13-31 35-32-35-62 



Chandelon 6 used for oxidising albumin, barium peroxide, which was 

 suspended in the solution and then decomposed by C0 2 . The nascent 

 hydrogen-peroxide changed the albumin into an acid substance, which 

 could be precipitated from alkaline solutions with acids. He further 

 obtained propeptone and peptones. 



Briicke 7 also discovered a peculiar acid giving the biuret reaction, 



1 That pure tryptophane gives Millon's reaction has been pointed out previously. 



2 Kutscher and Zickgraf, Sitzb. d. kgl. preuss. Akad. d. Wiss. 26th May 1903 ; 

 Zickgraf, Inaugural Dissertation, Marburg, 1904 ; Zeitschr. f. physiol. Chem. 41. 259 

 (1904). 



3 Bechamp, Leibig's Ann. der Chem. und Pharm. 10O. 247 (1856). 



4 Subbotin, Chem. Centralbl. 1865, p. 594. 



5 Pott, Journ. f. prakt. Chem. [2] 5. 355 (1872). 



6 Chandelon, Ber. d. deutsch. chem. Ges. 17. 2143 (1884). 



7 E. Briicke, Sitzungsber. d. Wien. Akad., Math.-naturw. Kl., III. Abteil., 83. 

 (1881), January and February. 



