CHEMICAL COMPOSITION OF PROTEIN MOLECULE 69 



I. Estimation of Amino Nitrogen. 



The estimation of the amino nitrogen is performed in an apparatus 

 very similar to that used by Sachsse and Kormann and by Horace 

 Brown and Millar ; the apparatus is filled with nitric oxide, which gas 

 is also used for washing the evolved nitrogen into the eudiometer ; 

 excess of nitric oxide is removed with permanganate contained in a 

 Hempel pipette. Fig. 2 shows the apparatus designed by Van Slyke. 



FIG. 2. 



Reproduced by kind permission from the Journal of Biological Chemistry. 



It consists of a vessel D of 35-37 c.c. capacity for the interaction of 

 the nitrous acid and the solution of the amino substance. Connected 

 with this vessel, which is fitted with a four-holed rubber stopper held 

 in place by a wire, or by an external screw stopper, are 



A, a vessel of 35 c.c. capacity to hold water for displacing air from 

 D, or receiving solution from D. 



B, a 10 c.c. burette containing the solution of the amino substance. 



C, the exit tube for the evolved gases ; its lower end is flush with 

 the stopper. It is connected with the gas burette F. 



