258 NITRATES. [CH. X 



Method based on the action of dilute acids. 



The solution is boiled for about one hour with 5 p.c. 

 sulphuric acid in a flask with reflux condenser, and the 

 ammonia produced is estimated either gasometrically by 

 sodium hypobromite in a nitrometer, or by distillation with 

 magnesia into a measured volume of standard acid. 



With asparagin the reaction is 



C4H8N,03 + H,0 = C,H,N04 + NH3. 



Therefore in this process 14 grs. nitrogen = 132 grs. 

 anhydrous asparagin (or 17 gi's. ammonia = 132 grs. 

 asparagin). 



For details of the estimation of 'combined ammonia/ 

 see Sutton, Volumetric Analysis, pp. 59 and 482. 



[The gasometric process in the nitrometer is carried 

 out as in the estimation of urea by sodium hypobromite.] 



Estimation of Nitrates and Nitrites. 



(a) Evaporate 100 c.c. to 5 c.c. (about) on the 

 water-bath. 



Decompose in the nitrometer with strong sulphuric 

 acid over mercury and measure the volume of nitric 

 oxide. This gives the NO from nitrites and nitrates 

 [reduce volume to 0° and 760 mm.]. 



[See Sutton, pp. 226 and 362.] 



(y8) In another portion of original solution (diluted 

 with pure distilled water if much nitrite is present), 

 estimate the nitrite by Griess' colorimetric method. 



Calculate the vol. of NO from nitrite (at 0° and 

 760 mm.) in 100 c.c. of original, and subtract this from 



