PROTEIN. 11 



xautlio-proteic acid, a change which is not produced by the action 

 of that reagent upon chlorod-proteic acid. 



Let us now revert to the undissolved residue, which ultimate- 

 ly assumes a uniform composition expressed by the formulai 

 C H . N O, . It is this which is first formed from protein by 

 the influence of the oxygen of the atmosphere. The other sub- 

 stance (tritoxide of protein) originates from it by the addition 

 of another equivalent of oxygen. In this respect albumen and 

 fibrin give different results. Albumen, without going through 

 this preparatory change like fibrin, is at once converted into trit- 

 oxide of protein by ebullition, the insoluble portion which re- 

 mains being unaltered albumen. 



From the composition of this insoluble portion it has received 

 the name of biuoxide of protein. It exists ready formed in the 

 huffy coat of the blood. Von Laer has obtained it from hair 

 in the following manner. The protein is first thi'own down 

 by the addition of a little acetic acid to a solution of hair in 

 potash. On the addition of a larger proportion of free acid, 

 after the removal of the protein, another substance, previously 

 in a state of solution, is thrown down. This is the biuoxide of 

 protein. Yon Laer describes it as a bright yellow precipitate. 

 After being carefuUy washed and dried it forms a black, glossy 

 resinous mass, which on being pulverized forms a dark amber- 

 yellow powder. 



It is insoluble in water and alcohol, but dissolves perfectly 

 in dilute acetic, hydrochloric, nitric, and sulphuric acids. It 

 does not assume so strong a yellow colour as protein, when 

 treated with nitric acid. 



Ferrocyanide and ferridcyanide of potassium, and acetate of 

 lead precipitate it from its acid solutions. It is soluble in potash 

 and ammonia. 



If the biuoxide of protein be treated with chlorine there is 

 formed, at a loss of one atom of nitrogen, and a gain of three 

 of oxygen, a new substance C^,, Hg^ N^ O^., to which no name 

 has yet been assigned. 



In order to obtain these products of oxidation of protein by 

 boibug fibrin in water, it is essentially necessary that there 

 should be free access to the atmospheric air. 



' See Appendix I, Note 3. 



