148 
DETERMINATION OF NITROGEN. 
the ammonia, moderate the absorption by the acid, and thus 
completely prevent the rise in the tube of combustion. 
After the tube is carried to red heat by degrees, through- 
out its whole length, and the disengagement of gas ceases 
completely, which takes place when all the carbon set free is 
oxidized, that is when the mixture becomes white, the poste- 
rior turned up end of the tube of combustion is to be broken, 
and several times its bulk of atmospheric air is to be inspired 
by means of the absorption apparatus, so as to draw through 
it all the ammonia which yet remains in the tube. This 
inspiration of the air may be affected by means of the potassa 
apparatus, placed at the point g of the absorption apparatus, 
by which means the acid vapors following the current of air 
are completely obviated. 
The restoration of its white color to the mixture in the 
tube of combustion, is an essential condition, for the ammonia , 
in contact with an alkali and carbon at a high temperature, 
readily forms hydrocyanate of ammonia, and consequently 
cyanogen, which involves a loss of azote in the experiment. 
But if the heat be sufficiently high, all the carbon is burnt, 
and there is no fear of the formation of cyanogen. 
By this process all the nitrogen in solid organic matters, 
may be changed into ammonia. The number of liquid or- 
ganic matters containing nitrogen, are not considerable; 
nevertheless their combustion does not offer other difficulties, 
and the quantity of nitrogen may be determined by our me- 
thod with as much exactness as the solid combinations, sup- 
posing, nevertheless, that the nitrogen does not exist as nitric 
acid. 
We proceed with liquids precisely as in their combus- 
tion with oxide of copper : a little of the mixture of soda 
and lime is placed in the tube, then the bulb containing a 
known quantity of the substance, the point being previously 
broken, then fill the tube with the alkaline mixture, and final- 
ly theasbestus plug. 
The most certain and most regular mode of operating, is to 
heat first the anterior third of the tube, and then to drive off 
