146 PRACTICAL ORGANIC AND BIO-CHEMISTRY 



(2) By estimation of the animo nitrogen. 



Van Slyke has shown that amino acids can be readily estimated by the 

 measurement of the volume of nitrogen evolved by the action of nitrous acid 

 according to the equation : 



+ HNCX 



:OOH 



COOH 



N 2 + H 2 0. 



Half of the volume of nitrogen evolved corresponds to the amount of 

 nitrogen in the amino acid. 



The apparatus required is shown in Figs. 33 and 34. 



FIG. 33. 

 From the J. Biological Chemistry, 1912, 12, 278. 



It consists of the deaminising bulb D, of 40-45 c.c. capacity, to which are 

 fused (i) a tap d for purposes of emptying it ; (2) a cylindrical vessel, A, of about 

 35 c.c. capacity with a mark at 7 c.c. and tap a ; (3) a 10 c.c. burette, B. The. 

 glass tubing is strong walled and of 3 mm. diameter, and the bores of the 

 taps should also be 3 mm. The connection between D and B should be 

 at least 8 mm. inner diameter so as to allow free circulation. The bulb 



