PROTEIN. 9 



alkalies it forms dark red soluble salts, and metallic salts throw 

 down yellow precipitates. In a state of combination, tlie for- 

 mula for this acid is C^^ H„, N, O,,: when free it contains 

 two atoms of water. 



The changes which occur in the production of this acid may 

 be illustrated by the equation — 



^. Chlorine and protein. On passing a current of chlorine gas 

 through a solution of any of the protein-compounds, (albumen, 

 fibrin, or casein,) a white flocculent precipitate is thrown down. 

 After washing it, and carefully drying it at a temperature of 

 212°, Mulder deduced from it the formula C^„ H^^ N^ O,, + Cl O3. 

 He termed it cJiloro-proteic acid. It appears from his investi- 

 gations that the protein remains unchanged, but that a portion 

 of the water is decomposed, and that its oxygen combines with 

 chlorine to form chlorous acid (Cl O,) while its hydrogen com- 

 bines with another portion of chlorine to form hydrochloric 

 acid (H Cl) which remains in solution in the water. ^ 



When ammonia is added to the chlorod-proteic acid, the 

 latter substance dissolves, and gives off a large amount of nitro- 

 gen. The solution must be evaporated to dryness, and then 

 treated with warm water, which takes up a portion of the residue. 

 On the addition of alcohol to this aqueous solution, a precipitate 

 is thrown down, while muriate of ammonia remains in solution. 

 This precipitate is composed of a substance of great phj'siolo- 

 gical interest. Its formula^ is C^^ H^^ N,_ O^^ + HO. Mulder 

 originally termed it oxyprotein, but he has recently given it the 

 more descriptive name of tritoxide of protein, without however 

 intending to imply anything more than that it contains three 

 atoms more oxygen than protein. There is another and, in 



' That this compound is a chlorite of protein and not a chloride of tritoxide of 

 protein seems certain from its analogy with a corresponding compound of gelatin. 

 ^ See Appendix I, Note 2. 



