CHAPTER III. 



Analytical Methods. 



DETERMINATION OF TOTAL NITROGEN IN CYANAMID. 



Practically all the Cyanamid manufactured in this country 

 prior to January i, 1912, contained about 23 per cent, of its 

 total nitrogen in the form of nitrates. Hence, for the deter- 

 mination of total nitrogen in such Cyanamid it is necessary to 

 use a method that will determine nitrate nitrogen as well as 

 nitrogen derived from Cyanamid. For this purpose the Official 

 Gunning method, modified for nitrates, is suitable. The 

 period of digestion should be at least five hours. The influ- 

 ence of the period of digestion is shown in the following values 

 obtained on a sample of Cyanamid containing nitrates: 



Per cent, nitrogen 



2 hours digestion 15.61 



3 " " 15.76 



4 " " 16.03 



5 *' " 16.06 



All the Cyanamid manufactured in this country since Jan- 

 uary I, 1912, is free of nitrates, and therefore, the simple 

 Kjeldahl or Gunning method may be used. The Gunning, 

 which is in general use, is carried out as follows : 



REAGENTS REaUIRED. 



N/2 (Half-normal) Sulphuric or hydrochloric acid. 



N/io (Tenth-normal) Sodium hydroxide, or ammonium 



hydroxide. 

 Sulphuric acid, C. P., specific gravity 1.84. 

 Sodium hydroxide, saturated solution. 

 Potassium sulphate, C. P. 

 Cochineal indicator. 



To determine nitrogen weigh out 0.7 gram of finely ground 

 sample. Each cc. of half-normal acid is equivalent to i per 



