236 CHEMISTRY OF THE PROTEIDS CHAP. 



albumins are similar bodies containing a large amount of halogen, 

 which is, however, readily split off. 



Habermann and Ehrenfeld l and Panzer 2 have allowed nascent 

 chlorine to act on albumins, when one part of the albumin is 

 dissociated, while another portion, still albuminous in nature, has 

 chlorine substituted for hydrogen. This substituted product contains 

 no sulphur, is strongly acid, and of a reddish brown colour. (See 

 also p. 96.) 



The brominated and chlorinated albumins are, also, brown or 

 greyish powders resembling the corresponding iodine-compounds as 

 regards solubility, precipitation, and colour reactions. The same 

 holds good for their behaviour during metabolism ; physiologically 

 they are indifferent or produce the same effect as would the corre- 

 sponding chlorine and bromine salts. Nothing is known regarding 

 their occurrence in nature, apart from a remark of Drechsel's, that 

 a chlorinated albumin exists along with an iodo-albumin in the 

 skeleton of Gorgonia. 



Nitro-substitution Products 



Just as it is possible to introduce halogen -radicals into the 

 albumin-molecule, so is it possible to substitute nitro-groups, as was 

 done first by Low, 3 and quite recently in a very thorough manner 

 by v, Fiirth. 4 Low 3 calls his products tri-nitro- albumin and 

 hexanitro-albumin-sulphonic acid. By adding urea to the nitrous acid 

 and so preventing the formation of nitric acid, v. Fiirth obtained a 

 nitro-casein having the following percentage composition : 



C H N N0 2 S P O 



52-6 6-69 15-87 1'78 0'64 0'56 23-64 



Without the addition of urea a progressive dissociation takes place, 

 xanthoprotein being formed, besides large amounts of albumoses and 

 peptones, which generally are also nitrated. We therefore meet 

 with the same changes as when we studied all the other dissociation- 

 products on p. 94. The xanthoprotein and the other nitro-substitu- 

 tion products are acid in character and possess a yellow colour which, 

 on adding a fixed alkali, is converted into a reddish-brown. The 

 xanthoproteic reaction depends therefore on the formation of nitro- 



1 J. Habermann and K. Ehrenfeld, Zeitschr. f. physiol. Ghem. 32. 467 (1901) ; 

 R. Ehrenfeld, ibid. 34. 566 (1902). 



2 T. Panzer, ibid. 33. 131 (1901), 33. 595 (1901), 34. 66 (1901), 35. 84 (1902). 



3 0. Low, Journ.f. prakt. Cheat. [2] 3. 180 (1871), '[2] 5. 433 (1872). 



4 0. v. Fiirth, Einwirkung von Salpetersaure auf Eiweissstoffe, Habitations - 

 schrift, Strassburg, 1899 (here also the older literature). 



