PAPERS OX CHEMISTRY AND PHYSICS 317 



ates, an aliquot of clear extracted solution was taken and 

 titrated against a standard alkali (.1484 normal), using 

 Methyl-red-Para-nitro-phenol for the indicator. The fig- 

 ures for relative titrations are given in Tables 2. 3, and 

 4 (last column). They show that fertilizing materials 

 alone do not reduce the concentration of nitric acid to 

 any appreciable extent. (Table 4.) The fertilizing ma- 

 terials after they are applied to brown silt loam, as re- 

 corded in Table 3, reduce the acid concentration rather 

 uniformly to about 90 percent of its original strength. 

 This in no way accounts for the reduction of phosphorus 

 recovery to about 50 or 60 percent of its recovery from 

 fertilizing materials themselves. The titrations recorded 

 in Table 2 explain the failure of phosphorus recovery in 

 only a very limited number of cases. The soil number 

 "3", or the subsoil layer of brown silt loam, contained 

 a large amount of carbonates, which used practically all 

 of the acid present, thus making the phosphorus extrac- 

 tion impossible. Perhaps samples Nos. 21 and 24 also be- 

 haved in a similar way. With these three exceptions, 

 however, the reduction in the acid concentration fails 

 entirely to explain the behavior of phosphorus in all these 

 soils. The lack of such correlation is very apparent, if 

 one compares the surface soil with its subsurface and 

 the subsoil layers in regard to the phosphorus extraction 

 and the concentration of nitric acid at the end of the ex- 

 traction. 



Peat, or samples Xos. 40, 41, and 42, afford an inter- 

 esting observation. The carbonates of the surface layer 

 reduce the acid concentration to about one-sixth of its 

 original strength. In spite of that, the phosphorus re- 

 covery was practically complete. In the subsoil layer, 

 number 42, the acid concentration was over four times 

 as great as in the surface layer, yet the phosphorus re- 

 covery was reduced to 70 percent. Again, with the acid 

 in the subsurface layer, number 41, slightly weaker than 

 that in the subsoil layer, the recovery was complete. 

 There was even some stimulating effect noticed on the 

 soil phosphorus. 



Very little or no correlation could be traced if one com- 

 pares, in this respect, the surface, subsurface or the sub- 



