22 CYANAMID — MANUFACTURE, CHEMISTRY AND USES 



by the sulphocyanate or other convenient method. One atom 

 of silver corresponds to one atom of nitrogen. 



In both the Caro and Brioux methods, however, from 25 to 

 30 per cent, of the urea present is precipitated in caustic potash 

 solution as silver salts along with the dicyandiamide.^ Since 

 Cyanamid frequently contains more urea than dicyandiamide 

 this occasions considerable error. Henschel^ found that by the 

 Caro method about 7 per cent, of the nitrogen as dicyandiamide 

 was converted to other forms, presumably by the action of the 

 hot caustic alkali in boiling off the the ammonia. The total 

 nitrogen was not diminished, hence the urea (?) nitrogen was 

 increased at the expense of the dicyandiamide. 



Determination of Urea. — Caro determines the total nitrogen 

 remaining in the filtrate from the dicyandiamide separation and 

 designates it as urea. Since, however, some of the urea is 

 precipitated along with the dicyandiamide and since the filtrate 

 may also contain other derivatives, the method can hardly be 

 considered as satisfactory. Caro also recommends Liebig's 

 titration method for the determination of the urea in the 

 filtrate. Ulpiani,^ however, claims that the mercuric nitrate 

 used for the precipitation of urea in this method, also pre- 

 cipitates cyanamide and dicyandiamide, if present, dicyandia- 

 midine, amidodicyanic acid, ammonia, ammonium salts, and 

 probably all nitrogen compounds found in lime-nitrogen. 

 Ulpiani suggests the direct solution of the sample of lime- 

 nitrogen or Cyanamid with alcohol, but since dicyandiamide as 

 well as urea is soluble in alcohol, this procedure would not 

 simplify the problem very much. 



The question of analysis of cyanamide derivatives is much 

 in need of scientific study, but for the present it will be 

 sufiicient for most purposes to determine total nitrogen in a 

 given sample of Cyanamid, then to determine cyanamide and 



^ Brioux, loc. cit. 



' Georg Henschel, Das Verbal ten des technischen Calciumcyanamides 



bei der Aufbewabrung sowie unter dem Einfluss von Kulturboden 



und KoUoiden — Diss. Univ. Leipzig. 191 2. 

 ^ Ulpiani, loc. cit. 



