CH. X.] 



NON-PROTEIN NITROGEN. 



26l 



Method. To about 20 cc. of distilled water in a 50 cc. volumetric 

 flask add 5 cc. of recently drawn blood and mix by gentle agitation. 

 Add 3 cc. of the freshly prepared solution of metaphosphoric acid 

 and mix. Full up to the mark with distilled water, mix and transfer 

 the contents to a 100 cc. flask. Shake vigorously at intervals for at 

 least 5 minutes, or allow the mixture to stand for a longer period. 



Fig- 34- 



Apparatus for Micro- Kjeldahl by 

 Cole's modification. 



Tube for 

 titrating in a CO. 

 free atmosphere. 



Filter into a dry tube through a dry paper. The filtrate should be 

 crystal clear ; if it is not, it must be passed through the filter till 

 clear. Transfer 10 cc. of the filtrate to a boiling tube (about 

 7x1 in.), add 2 cc. of pure sulphuric acid and cautiously concen- 

 trate to a small volume over a free flame.* This is a rather tedious 



* See Langstroth, Journ. Biol. Chem., xxxvi., p. 377. 



