CYANAMID — MANU]?ACTURE:, CHE^MISTRY AND USEJS 97 



permanganate method described in Bureau of Chemistry, U. 

 S. Department of Agriculture, Bulletin 107, page 10. In this 

 method a sample of fertilizer containing about 0.075 grams of 

 nitrogen is digested for 30 minutes on a water or steam bath 

 with 125 cc. of potassium permanganate solution containing 2 

 grams of potassium permanganate. It is then diluted with 

 100 cc. cold water and filtered and washed until the total filtrate 

 amounts to 400 cc. The nitrogen is determined in the residue ; 

 the percentage of nitrogen removed is called the availability. 

 To obtain the effect of the potassium permanganate this 

 method was used, first, with 125 cc. of distilled water in place 

 of the permanganate, and second, with the 125 cc. of perman- 

 ganate solution. 



Per cent. 



Availability with water in place of permanganate 94.34 



Availability with permanganate 87.54 



Since the only difference in the above experiments was the 

 absence of the 2 grams of potassium permanganate in the first 

 run, it is evident that potassium permanganate has the effect 

 of converting about 7 per cent, of the total nitrogen into in- 

 soluble compounds. 



Alkaline Permanganate Method. — In this method the avail- 

 ability is measured by the amount of ammonia that is formed 

 and distilled from an alkaline permanganate solution. An 

 amount of sample containing 0.045 grams of nitrogen is 

 digested below the boiling point with 100 cc. of solution con- 

 taining 15 grams of sodium hydroxide and 1.6 grams of 

 potassium permanganate, for thirty minutes. It is then boiled 

 and the distillate collected until 85 cc. is obtained. The per- 

 centage of nitrogen distilled over as ammonia represents the 

 availability. In order to learn the effect of each reagent a run 

 was made by this method using, first, 100 cc. of distilled water 

 in place of the alkaline permanganate solution; second, a run 

 was made with 15 grams of sodium hydroxide in 100 cc. of 

 solution, and a third run was made with both sodium hydroxide 

 and potassium permanganate in 100 cc. solution. The results 

 were as follows : 



