OFFICIAL RUFFLE METHOD 343 



cool below redness to avoid any danger of acting on the nitrogen 

 in the air. 



304. The Ruffle Soda-Lime Method. Many attempts have 

 been made to adapt the soda-lime method to the determination of 

 nitric nitrogen. Of these, the process devised by Ruffle is the only 

 one which has proved successful. 91 The method is founded on 

 the action of sulfurous vapors on the nitrogen oxids produced dur- 

 ing the combustion, whereby sulfuric acid is formed and the 

 nascent nitrogen is joined with hydrogen to form ammonia. By 

 this process all the nitrogen contained in the sample, even if in 

 the nitric form, is finally obtained as ammonia. In the original 

 method the reagents employed were sodium thiosulfate, soda- 

 lime, charcoal, sulfur, and granulated soda-lime. Subsequently, 

 the official chemists substituted sugar for the charcoal. 92 The 

 method was used for a long time by the official chemists and 

 came into general favor until displaced by the simpler and 

 cheaper processes of the moist combustion method adapted to 

 nitric nitrogen. As finally modified and used by the official chem- 

 ists, the process is conducted as described below. 93 



305. The Official Ruffle Method. Reagents and Apparatus. 

 (i) The standard solutions and indicator are the same as in 

 the kjeldahl method. 



(2) A mixture of equal parts by weight of fine-slaked lime 

 and finely powdered sodium thiosulfate dried at 100. 



(3) A mixture of equal parts by weight of finely powdered 

 granulated sugar and flowers of sulfur. 



(4) Granulated soda-lime, as described under the soda-lime 

 method. 



(5) Combustion tubes of hard Bohemian glass 70 centimeters 

 long and 1.3 centimeters in diameter. 



(6) Bulbed U-tubes or Will's bulbs, as described under the 

 soda-lime method. 



Manipulation. (a) Clean the U-tube and introduce 10 cubic 

 centimeters of standard acid. 



(b) Fill the tube as follows: (i) A loosely fitting plug of as- 



91 Journal of the Chemical Society, 1881, 39 : 87. 



K Division of Chemistry, Bulletin 16, 1887 : 51. 



98 Division of Chemistry, Bulletin 46, Revised Edition, 1899 : 19. 



