98 CYANAMID — manufacture:, CHEMISTRY AND USES 



Per cent. 



Availability with water alone 13.79 



Availability with water and sodium hydroxide 53.90 



Availability with water and sodium hydroxide and 



potassium permanganate 4.75 



This experiment shows that the nitrogen in Cyanamid is only 

 slowly converted into ammonia by the action of boiling water 

 alone, and that it is much more rapidly converted into ammonia 

 in the presence of sodium hydroxide. By the action 

 of potassium permanganate, however, the formation of 

 ammonia is almost completely prevented, even in the presence 

 of sodium hydroxide. 



Hence, in the above methods the addition of potassium per- 

 manganate has the opposite effect from what was intended to 

 be the function of potassium permanganate, namely to make 

 insoluble compounds soluble and to convert complex com- 

 pounds to the ammonia form. In the case of Cyanamid, the 

 neutral permanganate method makes some water-soluble com- 

 pounds insoluble, and the alkaline permanganate method practi- 

 cally prevents the formation of any ammonia. 



The method which is lately coming into favor is the modified 

 alkaline permanganate method adopted by the Agricultural 

 Experiment Stations of New York, New Jersey and the New 

 England States on March 4, 191 1. 



Modified Alkaline Permanganate Method. — This differs from 

 the other methods in that an amount of sample equivalent to 

 0.050 grams of nitrogen is first washed on a filter with distilled 

 water at room temperature until 250 cc. of filtrate is obtained. 

 This is intended to remove all the water-soluble nitrogen. As 

 a matter of fact, it removes about 87 per cent, out of a possible 

 94 per cent, of water soluble nitrogen in a low-grade Cyanamid, 

 and about 89 per cent, out of a possible 96 per cent, in a high- 

 grade Cyanamid. The ''insoluble" residue is digested for thirty 

 minutes in a flask with 120 cc. of solution containing 2.5 grams 

 potassium permanganate and 1.5 grams sodium hydroxide, and 

 the ammonia is then distilled by boiling until 95 cc. of distillate 

 is obtained. The sum of the percentage of water soluble nitro- 



