168 CHEMISTRY OF FARM PRACTICE 



from muriate of potash. The phosphoric acid is to be 

 derived from 16 per cent acid phosphate. 



This calculation should be handled as follows: The 

 number of pounds of plant food req aired for a ton of this 

 material is nitrogen equivalent to 80 pounds of ammonia, 

 160 pounds of actual phosphoric anhydride (P2Os), and 

 80 pounds of water-soluble potash. There is a specified 

 amount of one material to be used as a source of nitrogen, 

 150 pounds of nitrate of soda which will contain nitrogen 

 equivalent to 18 per cent of ammonia or 27 pounds in the 

 150 pounds of material. Nitrogen equivalent to 80 pounds 

 of ammonia is required; so 27 pounds furnished by the 

 nitrate of soda must be deducted, leaving 53 pounds to be 

 furnished by ground fish scrap which contains nitrogen 

 equivalent to 10 per cent of ammonia; hence it will require 

 530 pounds of ground fish scrap to furnish the remainder 

 of the nitrogen. In addition to the nitrogen content of 

 the fish scrap, this material carries 6 per cent of phosphoric 

 acid, which is equivalent to 31.8 pounds of phosphoric acid. 

 The amount of phosphoric acid required is 160 pounds, less 

 32 pounds derived from the ground fish scrap, leaving 128 

 pounds of actual phosphoric anhydride to be furnished by 

 16 per cent acid phosphate. The number of hundred 

 pounds of acid phosphate required can be determined by 

 dividing the number of pounds required, 128, by the num- 

 ber of pounds of phosphoric anhydride contained in 100 

 pounds of acid phosphate, 16, in this case. The number 

 of hundred pounds of muriate of potash to use is determined 

 by dividing 80, the number of pounds of actual potash, by 

 48, the number of pounds of potash contained in 100 pounds; 

 80^48 = 1.666, or 167 pounds. This form of calculation is 

 the one most used by fertilizer manipulators in calculating 

 their formulas. 



