COTTON CULTURE 75 



(e) Potash as Sulfate means simply sulfate of potash. 

 (/) Potash Equal (or equivalent) to Sulfate of Potash 



is an expression which means simply sulfate of potash. 



(g) Sulfate of Potash signifies that this compound 

 is actually present in the fertilizer, and that there is no 

 muriate present. 



(h) Potassium Oxide means the same as potash, or 

 actual potash. 



PHOSPHORIC ACID 



(a) Phosphoric Acid, as used in connection with fer- 

 tilizers, is a compound containing phosphorus and oxygen, 

 which in fertilizers is never found by itself, but in combi- 

 nation with lime. Phosphoric acid stands for a certain 

 amount ot phosphate of lime. We may say roughly that 

 one part of phosphoric acid is equivalent to about two 

 parts of phosphate of lime. 



(6) Soluble Phosphoric Acid represents the amount of phos- 

 phate of lime that dissolves easily in water. It is formed 

 by treating with sulfuric acid some form of insoluble 

 lime phosphate, such as bones, phosphate rock, etc. The 

 phosphate thus formed is readily soluble in water. 



(c) Reverted Phosphoric Acid is formed from solu- 

 ble phosphoric acid under certain conditions into which 

 we need not inquire here. Suffice it to say that the solu- 

 ble compound of phosphoric acid often changes to some 

 extent, on standing, into a form which, while less soluble, 

 is still quite readily available as plant food. 



(d) Available Phosphoric Acid includes both the solu- 



