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 



C 4 H 8 N 2 3 + H 2 = C 4 H 7 NO 4 + NH 3 . 



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

 anhydrous asparagin (or 17 grs. 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 and 760 mm.]. 



[See Sutton, pp. 226 and 362.] 



(/3) 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 and 

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



