E. J. Russell and J. A. Prescott 



105 



Table IX [continued) 



Soil, Agdell. Time = 3 hours. 



* Sufficient to make the - NO3 radicle up to N concentration. 



Phenol, cresol, toluene and alumina, so far from increasing, actually 

 reduce the amount of P2O5 brought out by nitric acid, and therefore 

 check the direct solvent action or increase the adsorptit)n. The following 

 experiment shows that the adsorption is increased. 50 gms. of the 

 soil Agdell A, which had been extracted with dilute sulphuric acid to 

 remove most of the soluble phosphate, was treated with 1 litre of dilute 

 HCl (-06 N) containing 25 % of ethyl alcohol, and a known amount of 

 sodium phosphate was added. The following amounts of P2O5 were 

 found : they are calculated as mgms. per 100 gms. of soil : 



All substances do not behave like this however: Table X shows that 

 pyrogallic acid is without effect, and that potash-alum and ammonium 

 oxalate considerably increase the solvent action. These latter sub- 

 stances, however, give rise to sulphuric acid and oxalic acid respectively, 

 both of which have greater net solvent power than nitric acid. In 

 reducing the adsorption of P2O5 it is obvious that our only hope would 

 be to light on something which is adsorbed in preference to P2O5, and 

 for the moment we have nothing but chance to guide us in the search. 



