CHAPTER XI. 



Permanganate Availability of Cyanamid. 



In order to have a ready means of determining the agricul- 

 tural availability of the nitrogen in various organic compounds, 

 certain chemical methods have been adopted that approxi- 

 mately measure this property. The permanganate availability 

 methods are in general use for this purpose. It is generally 

 assumed that nitrogen compounds soluble in water are readily 

 utilized as plant food, but it is also recognized that nitrogen 

 compounds insoluble in water may be utilized by the plant in 

 the course of growth. It seems to be generally true of organic 

 nitrogenous compounds that the solubility in water, together 

 with the relative ease with which the insoluble parts are de- 

 composed by potassium permanganate bears a regular relation 

 to the agricultural availability of the fertilizer. It is interest- 

 ing to examine whether Cyanamid takes its proper place in the 

 permanganate availability series of values as compared with its 

 agricultural availability, and which of the permanganate 

 methods gives the truest results. 



The following experiments on the solubility of Cyanamid 

 nitrogen in water, and its behavior under the influence of 

 potassium permanganate, were made under the direction of the 

 author in October, 19 12. The Cyanamid used was a low 

 grade, granulated material analysing as follows: 



Nitrogen 13-58 per cent. 



I.ime(CaO) 50.57 



Moisture i .83 ' * 



Carbon dioxide 4.00 " 



Size of granules 15 to 50 mesh 



EXPERIMENT I. 



Solubility on Filtej . — Samples of i gram, 2 grams, 4 grams 

 and 8 grams of granulated Cyanamid were placed on filter 

 papers and washed with successive portions of distilled water 

 at 25° C. until the volume of filtrate reached 250 cc. The 



