2IO CHEESE 



an ammonia distillation apparatus (p. 13), and excess 

 of magnesia added. 



The ammonia is then distilled into a known volume 

 of standard acid, and the amount of acid neutralised 

 estimated by titration as usual. 



Magnesia is employed in the place of potash or 

 soda, as these latter substances cause a hydrolysis to 

 ammonia of some of the amino-bodies present ; magnesia 

 does not act in this way. 



203. Determination of Nitrogen in Form of 



Amides. 



The value for the nitrogen in the form of amides 

 is obtained by subtracting from the total water-soluble 

 nitrogen (200 above) the soluble protein (201) and 

 the ammoniacal nitrogen (202). 



N % in form of amides = total water-soluble nitrogen % minus 

 N% in form of soluble protein minus 

 N% in form of ammonia and 

 ammonium compounds. 



204. Determination of Casein. 



The percentage of casein may be determined by 

 taking the difference between the percentages of total 

 nitrogen and water-soluble nitrogen and multiplying 

 the result by 6-38. 



According to the above method of analysis, the 

 nitrogen in cheese may be differentiated as follows : — 



Total nitrogen. 



Nitrogen in form of casein. 



Nitrogen in form of water-soluble proteins. 



Nitrogen in form of amides. 



Nitrogen in form of ammonia and ammonium 

 compounds. 



