PAPERS ON CHEMISTRY AND PHYSICS 



319 



CONCLUSIONS 



The foregoing data, it seams, justifies the following 

 conclusions : 



1. When phosphorus in the form of phosphatic ferti- 

 lizers is applied to ordinary mineral soils, it becomes con- 

 siderably less soluble in fifth normal nitric acid than 

 phosphorus of the same material before application. 



2. Peat soil, as an exception, does not depress the re- 

 covery of phosphorus under the same conditions. 



3. After phosphatic fertilizers are applied to the soil, 

 the recovery of phosphorus from soil treated with double 

 acid phosphate is not any greater than the recovery of 

 phosphorus from the same soil treated with natural rock 

 phosphate, using fifth normal nitric acid for the solvent 

 in each case. 



4. After the first extraction with fifth normal HX0 3 , 

 the subsequent extractions with fresh acid fail to extract 

 a considerable amount of additional phosphorus. Five 

 counsecutive extractions fail to recover the entire amount 

 of phosphorus applied either in the form of rock phos- 

 phate or double acid phosphate. 



TABLE 1. 

 Phosphorus content of phosphatic fertilizers used. 



Percent 

 Phosphorus 



Tennessee Rock Phosphate 13.8 



Double Acid Phosphate 19.94 



Slag A 8.40 



Slag B 9.30 



Slag C 5.79 



Slag D 6.61 



Birmingham Slag 8.55 



Blue Rock 13 .05 



Florida Soft Rock 14.77 



Apatite 12.36 



Iron Phosphate 16 . 36 



Aluminum Phosphate 17.09 



Acid Phosphate 9 . 54 



Steamed Bone Meal 14.81 



Amount of 

 material contain- 

 ing 4 mgs. of Phos. 



.0290 ems. 



.0201 " 



.0476 " 



.0430 " 



.0691 " 



.0605 " 



.0468 " 



.0306 •' 



.0271 " 



.0324 " 



.0244 " 



.0234 " 



.0419 " 



.0270 " 



