ACTION OF SUPERPHOSPHATES. 55 



sparingly soluble phosphate, regardless of the 

 nature of the soil. It is an unfounded idea, 

 that plants in the first stages of their growth 

 are nourished by the soluble phosphate, and, 

 during maturity, strengthened by the insoluble. 

 It would therefore be foolish, to say the least, 

 to prepare a superphosphate containing both 

 soluble and insoluble phosphoric acid. Exper- 

 ience has proved to satisfaction, that, of two 

 manures containing the same total amount of 

 phosphoric acid, the one with the largest amount 

 of soluble phosphate, other circumstances being 

 equal, is the most effective. 



" It is therefore indispensably necessary, espe- 

 cially in manufactories where mineral phos- 

 phates are worked, that the insoluble phosphate 

 be rendered as completely soluble as possible. 

 The manufacturer should at all times use every 

 effort to increase the amount of soluble phos- 

 phoric acid in his superphosphate. 



" If, on coming in contact with the soil, the 

 soluble phosphate become insoluble, why, say 

 the champions of pulverized coprolites, treat at 

 great expense mineral matters with acid, and 

 increase their cost, merely for the sake of again 

 obtaining in the soil insoluble products ? An- 

 swer : It is not the purpose of the acid alone to 

 produce soluble phosphate. The mineral first 

 of all is disintegrated by the acid, and then 



