DISTRIBUTION OF NITROGEN 93 



the tap c, which is turned so as to shut off this part of the apparatus 

 and to be in connection with D and the exit tube. 



7 c.c. of glacial acetic acid are put into A and run into D ; 30 c.c. of 

 the sodium nitrite solution 1 are placed in A and also run into D. 

 Sufficient should be used so that excess stands in A above the tap. 



The remaining air in the apparatus and that dissolved in the nitrous 

 acid solution is removed by closing c by a quarter turn, leaving a open 

 and shaking D. Rapid evolution of nitric oxide occurs which gathers 

 in D and forces 10-15 c.c. of solution back into A. The cock c is now 

 again opened and the nitric oxide, together with the air swept out of 

 the solution, is forced out of D by liquid from A through c. This 

 process is repeated twice to ensure removal of all the air. 



By closing c and shaking D a gas space of about 20 c.c. is now 

 made to make room for the amino solution from B. 



Tap a is closed and tap c is opened to connect D and F. These 

 manipulations require about two minutes. 



(2) Decomposition of the Amino Substance. 10 c.c. or less of the 

 solution to be analysed is put into the graduated tube B ; any 

 excess can be run off. The desired volume is run into D. The 

 burette B need not be graduated and the desired volume can be in- 

 troduced with a pipette into B, run into D, and B washed with a 

 little water, which is also run into D. The evolution of nitrogen 

 commences immediately, and D is thoroughly shaken for three to five 

 minutes to complete the evolution of the gas. Only in a few cases is 

 longer shaking necessary. 



The evolved gas passes into the burette F ; the residual gas in the 

 bulb is driven into F by opening the tap a and letting liquid run from 

 A into D as far as the tap c. 



(3) Absorption of Nitric Oxide and Measurement of the Nitrogen. 

 The tap of the burette F is turned to connect it with the Hempel 

 pipette and the gas is driven from F into the Hempel pipette by raising 

 the levelling bulb. By shaking the gases with the permanganate the 

 nitric oxide is absorbed. The residual nitrogen is run back into F, 

 the permanganate filling the tubing as far as the tap^C The volume 

 of gas in F is then measured by bringing the surface of the liquid in 

 the bulb even with the meniscus. Generally, one shaking with the 

 fresh permanganate suffices to remove all the nitric oxide, but it is ad- 

 visable to test if the absorption is complete by returning the gas to the 

 Hempel pipette and again measuring. The weight of nitrogen corre- 



1 30 grams per 100 c.c. 



