82 MANUFACTURE OF FERTILIZING MATERIALS 



per cent of phosphoric acid and 9.2 per cent of 

 nitrogen, together 18 per cent, but after the sec- 

 ond crushing the product uniformly shows 9 per 

 cent of phosphoric acid and 9 per cent of nitro- 

 gen. This method of preparation serves, equally, 

 for all the mixing if desired to make superphos- 

 phate of ammonia 5 XlO. For 100 kg. of mixture, 



100 X5 



take =24.4 kg. of sulphate of ammonia 



^jU.o 



of 20.5 per cent N, and consequently 75.6 kg. of 



100 X 10 



superphosphate containing - - = 13.2 per cent 



75.6 



phosphoric acid. If it be a case of a wagon of 

 10 tons of sulphate of ammonia, 41 tons of the 

 mixture will be obtained of the 5x10 mixture, re- 

 quiring consequently 31 tons of superphosphate. 

 It is easy to bring the superphosphate to the right 

 strength by mixing it with a high, grade super- 

 phosphate, or with gypsum free from iron, alu- 

 mina, and carbonate of lime. The low, grade 

 superphosphate and gypsum act in the nature of 

 a "filler." 



In regard to the manufacture of superphosphate 

 of ammonia and potash, this is prepared in the same 

 way. Suppose it is desired to prepare a mixture of 

 this nature with 5 per cent of nitrogen, 7.5 per cent 

 of potash, and 9 per cent of phosphoric acid, and 

 that there was to be used for the purpose sulphate 

 of ammonia with 20.5 per cent N, and potash 

 salts with 37 per cent K. To get 100 kg. of super- 

 phosphate of ammonia and potash it is therefore 



