PRACTICE IV 



DETERMINATION OF NITROGEN IN REAGENT? 



Measure out exactly 10 cc. of the concentrated alkali in a beaker 

 and dilute to 200 cc. with distilled water. Stir and add slowly, finally 

 drop by drop, concentrated sulfuric acid until the alkali is neutral- 

 ized, as shown by the change of color. 



10 cc. alkali are equivalent to cc. H 2 SO 4 



How many cubic centimeters of alkali are necessary to neutralize 

 20 cc. H 2 S0 4 ? 



Place approximately 2 g. of pure sugar in a Kjeldahl flask, add by 

 measure approximately .65 g. metallic mercury and 20 cc. sulfuric acid. 

 Digest in a ventilated hood .over a low flame till colorless, and while 

 still boiling hot carefully add powdered potassium permanganate 

 until the solution is green. Allow to cool. Add 200 cc. of ammonia- 

 free water, connect in the distillation apparatus, add carefully suffi- 

 cient concentrated alkali to neutralize 20 cc. of concentrated sulfuric 

 acid, shake until thoroughly mixed, and distill, using 10 cc. of 

 standard acid in the receiver. 



(1) Titrations cc. NH 3 



(2) Titrations cc. NH 3 



Av cc.NH 3 



Check up the standard ammonia solution by titrating against the 

 standard hydrochloric acid solution. 



Correction for nitrogen in reagents in terms of standard ammonia 

 solution cc. 



Explain the use of the sugar. Give the reaction between the sugar 

 and the sulfuric acid. Why is the mercury used ? the potassium per- 

 manganate ? the potassium sulfid ? 



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