KNKICUING SOIL— (^OMMEKCIAL RESOURCES 95 



Waters 11:0 ^ 



Lime V Phosphoric acid ; or, CaO v PjOj 

 Lime ) CaO \ 



This is di- (or two) calcic pliosphate. This is 

 iii<ohil»I«> in rnin-wator, })iit ln'ci^nios solultl<' in 

 tlic soil-water. 



145. If two parts of the lime be united with 

 sulfuric acid and their places be taken by water, 

 there remains : 



Water") H:.0^ 



Water v Phosphoric acid ; or, H-0 v PjOj 

 Lime \ CaO ) 



This is mono- (or one) calcic })hosphate. This 

 is readily soluble in soil water, but in the soil it 

 tends to become insoluble, or to revert to the 

 dicalcic form (and is then said to be "reverted"), 

 and some of it may eventually become tricalcie 

 and unavailable. The lime that is nMuoved by 

 the sulfurie acid unites with the sulfuric acid to 

 form calcium sulfate ; that is, phister or i^ypsum 

 (CaSO^). The dicalcic an<l mouocalcic are the 

 forms that are known as acid phosphate, and 

 sold in commercial fertilizers. 



4. potash {))otassium oxide, K^O) 



146. Next to phosphoric acid, potasli is the 

 most important mineral plant -foo<l. It is placed 

 after phosphoric acid in importance not be- 



