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plied. As nitrates are beneficial to plant life and nitrites 

 injurious and indicative of sewage contamination, it is im- 

 portant to ascertain qualitatively if there are any nitrates and 

 nitrites in the water used for irrigation and for drinking pur- 

 poses. Water containing nitrates, coming in contact with 

 sewage, the nitrates become reduced to nitrites. For nitrites the 



Metaphynelene diamine hydrochloride (C 6 tL. (^ ^' JJQ* 1 



test is the best. This reagent is dissolved in Sulphuric acid, 

 and a drop of it added to water supposed to be contaminated 

 by sewage. If yellow colour is gradually formed, the pre- 

 sence of nitrites is to be inferred. 



For ascertaining the presence of nitrates, an equal 

 volume of strong sulphuric acid should be added to a 

 volume of the water tested, and then the number of drops 

 of Indigo sulphate solution it decolourises, should be count- 

 ed. The solution should be heated and it should be seen 

 that a slight permanent colouration remains at the end. 



(5) The free ammonia in water is determined by Nessler's 

 test. 



(6) Albuminoid ammonia is due to nitrogenous or- 

 ganic bodies in the water. After the free ammonia has been 

 estimated, the residue remaining in the retort after distil- 

 lation with Sodium Carbonate is heated with a strongly 

 alkaline solution of Potassium Permanganate, sufficient 

 being added to make up about 500 c. c. The nitrogenous 

 matters undergo a limited oxidation and nitrogen is obtained 

 as ammonia. Then Nessler's test is applied to the distilled 

 liquor which is collected in portions of 50 c.c The alkaline 

 solution of Potassium Permanganate is prepared by dissolv- 

 ing 4 grammes of Potassium Permanganate and 100 grammes 

 of Potassium hydrate in 550 c. c. of distilled water. 



(7) Total residue is what remains behind after a sample 

 of water has been distilled. 



