M. Ville on the Estimation of Nitrogen. 459 



March Number of the Annates de Chimie et de Physique. When 

 a solution of nitrate is mixed with excess of a solution of proto- 

 chloride of iron and boiled, a portion of the iron is oxidized, and 

 at the same time a mixture of deutoxide of nitrogen and hydro- 

 chloric acid is disengaged. M. V^ille found that when deutoxide 

 of nitrogen, mixed with excess of hydi'ogen, was passed over 

 spongy platinum heated to redness, the whole of the nitrogen is 

 converted into ammonia, and this may be estimated by a stand- 

 ard solution. This method is applicable even where the nitrate 

 is mLxed with considerable quantities of organic matter. It can 

 be used for the determination of nitrates where the quantity of 

 nitrogen does not exceed a centigramme; but when a larger 

 quantity of nitrate is employed, losses are sustained which vitiate 

 the results. Coke washed w ith hydrochloric acid and calcined 

 in close vessels, Stenhouse's platinized charcoal, and spongy iron 

 may be substituted for the spongy platinum. 



If, instead of passing hydrogen and deutoxide of nitrogen over 

 spongy platinum, deutoxide of nitrogen and sulphuretted hy- 

 drogen be passed over soda-lime, the whole of the nitrogen is 

 converted into ammonia, which is estimated as above. This 

 method may be used for substances which contain a decigramme 

 of nitrogen. The reaction on which the method depends is thus 

 expressed : — 



3HS + NO^ + 2CaO = NH^ + CaO 80^ + CaS^ or CaS + S. 

 The execution of the method is simple, and does not take long. 

 The protochloride of iron and nitrate are placed in a flask fur- 

 nished with two tubes. Through one of these, which dips in 

 the protochloride, a current of hydrogen passes which serves to 

 expel all air from the apparatus. The other tube, by which the 

 deutoxide of nitrogen and hydrochloric acid pass off, is connected 

 with a second flask containing some j^otash which retains the 

 hydrochloric acid. By means of two other tubes, the second 

 flask is placed in connexion with an apparatus for generating 

 sulphuretted hydrogen, and with the combustion tube. The 

 combustion tube contains soda-lime, and afiixed to it is a bulb 

 apparatus for absorbing the ammonia. In making the analysis, 

 hydrogen is first passed through the apparatus till all the air is 

 expelled ; the combustion tube is then heated, and the current 

 of hydrogen having been moderated, the flask containing the 

 protochloride of iron and nitrate is gently heated. At the same 

 time sulphuretted hydrogen is passed over, so that 3 or 4 centims. 

 of the soda-lime may have become attacked at the time that 

 the disengagement of deutoxide of nitrogen commences. After 

 about ten minutes the action is complete : hydrogen is passed 

 through, the ajjparatus for absorbing the ammonia is detached, 

 and the ammonia estimated. 



2 H2 



