ESTIMATION OF NITRATES 



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apparatus is tight, water will rush up and fill the delivery 

 tube as far as the tap. 



The measuring tube is now fixed in position over the 

 end of the delivery tube and about 0-2 gram of sodium 

 nitrate (or 10 c.c. of the solution from 92 {b), p. 108) 

 dissolved in water and placed in the dropping funnel. 

 By carefully opening the funnel the nitrate is drawn 

 into the flask and the last traces similarly washed in 

 with a few c.c. of water, care being taken to prevent the 

 introduction of any air. The mixture is now heated 



Fig. 19. — Schlossing's apparatus for estimation of nitrates. 



carefully until a slight pressure is induced inside the 

 flask. The screw-clip is then opened and the contents 

 of the flask boiled until no more gas is evolved. The 

 measuring tube and its contents are transferred to a 

 cylinder of water and the volume of the nitric oxide 

 which has been collected read off after bringing the 

 water to the same level inside and outside the tube. 

 The volume of the gas is corrected for temperature 

 and pressure and the calculation of the percentage of 

 nitrogen made as in the nitrometer method {a). 



The collection of the gas should really be made over 



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