Superphosphate 9 



season; however, the phosphorus in raw rock 

 continues to become available, year by year, 

 until the total amount is drawn upon. For 

 cultural purposes the important question is 

 whether or not there is sufficient phosphorus 

 available in one season for the crop in ques- 

 tion; this, of course, depends upon many 

 factors which cannot be gone into here. 

 . Analysis of Rock Phosphate. — An analy- 

 sis of Tennessee rock phosphate taken from 

 the American Fertilizer Handbook for 1908 

 is here given: 



Per cent 



Moisture (loss on drying) 0.87 



Combined water and organic matter 



(loss on ignition) 1 . 53 



Sand and insoluble matter 2.76 



Ferric oxid, Fe203 2.40 



Almnina, AI2O3 1 . 99 



Lime, CaO 49.07 



Magnesia, MgO 0.24 



Carbon dioxid, CO2 1 . 08 



Fluorin, F 2.98 



Sulfur trioxid, SO3 1.03 



Phosphoric acid, P2O5 35 . 62 



99.57 



When these figures are put together in an 

 attempt to show the substances that existed 

 in the original rock the data shown under 

 colum (a) is obtaind. The composition of 

 another sample of rock phosphate is shown 



