COMPOUND MANURES 79 



nia is added during the "dissolving" of the super- 

 phosphate by dissolving this salt in the sulphuric 

 acid used to decompose the superphosphate, but 

 this method of proceeding is not applicable except 

 with small amounts of sulphate of ammonia. 



The process generally used in making super- 

 phosphate of ammonia is as follows: The dry 

 superphosphate of ammonia delivered in 10-ton 

 wagons, being stored and analyzed, the amount of 

 superphosphate and sulpnate required to give a 

 mixture of 9 X9 has been calculated. Suppose that 

 the sulphate of ammonia contains 20.5 per cent N, 

 then 20.5 kg. correspond to 100 kg. (NH 4 )2SO 4 , 

 9 kg. correspond therefore to 



=42 kg. (NH 4 )2S0 4 . 



There remains then for the superphosphate 

 100 -42 =58 kg. These 58 kg. of superphosphate 

 must contain 9 kg. of soluble phosphoric acid, which 



100X9 

 corresponds to - = 15.5 per cent phosphoric 



Oo 



acid. To make the mixture the 10 tons of sul- 

 phate of ammonia are laid in a heap 33 feet long 

 and on each heap the necessary portion of super- 

 phosphate to the total 12.77 tons. Two laborers 

 mix the two with the shovel, making the whole into 

 one heap and recommence the same in an inverse 

 direction. The mixer is then passed through a dis- 

 integrator or toothed crusher, then it is laid on a 



