244 



Biological Chemistry. 



They are very easily determined. A weighed amount of 

 a protein is hydrolyzed with acid. On completion of 

 hydrolysis the humin substance is filtered off. The 

 mother liquor, after evaporation to a small bulk, is made 

 alkaline with magnesium oxide, and the ammonia set free 

 is then distilled off in vacuo into an excess of standard 

 acid, and estimated by titration. The residue in the dis- 

 tillation flask is then acidified, and phosphotungstic acid is 

 then added ; this precipitates the diamino-acids. The 

 nitrogen is determined in the humin and phosphotungstic 

 acid precipitate, the nitrogen of the ammonia is deter- 

 mined, as already mentioned, by titration, whereas the 

 monoamino nitrogen is ascertained by difference, by deter- 

 mining the total nitrogen in the protein, and subtracting 

 the amount of " humin," " amide," and " diamino " nitrogen. 

 All nitrogen estimations are made by Kjeldahl's method. 



The following are some examples of the Haussmann 

 numbers : 



By carrying out the determination of the Haussmann 

 numbers on two proteins of different origin it is possible 

 to gain some idea as to whether they are identical or not. 



