Solubility 



difference may arise from the more or less violent 

 way in which they have been formed, from the very 



2. Phosphoric Acid in Basic Slag. Different Solubility, 



SAME Fineness, 



During the crop. 



Total phosphoric acid. 

 Fooy crop. 



Phosphoric acid soluble in 



weak acids. 



Good crop. 



• = Insoluble. O = Soluble. The general argument is that 

 the total phosphoric acid will act next year — perhaps. The likeli- 

 hood is that it will not — perhaps never. 



After the crop. 



The insoluble phosphoric The soluble has been as- 



acid remains in the soil similated by the plants, 



like this. 



Since phosphoric acid is not bought to lie idle in the soil, it 

 follows that total phosphoric acid should never be bought. 



high temperature which accompanied their forma- 

 tion, from their more or less recent formation, or from 

 the physical form in which they are presented, and 



21 



