E. J. Russell and J. A. Prescott 



81 



The equations obtained and the meaning of the constants. 



18. The following equations have been obtained expressing the 

 equilibrium obtained in the adsorption of PgOg by soils in the presence 

 of various acids : 



Heavy soils. Rothamsfed. 



Lighter soils. Saxmundham. 



N/IO HNO3 . Time = 2 hours 

 Plot 4 (2 cwt. superphosphate annually) ... 

 Plot 6 (unmanured) ... 



... y= 7-9 0.2-7 

 ... y^ G-3C2-0 



Wohurn. 



N/10 HNO3 . Time = 1 hour 

 Stackyard wheat plots (unmanured) 



Lightest soil. Bramford^. 

 N/IOHNO3. Time::=l hour 



7/=30-7C6-2 



y= 2-7C2-6 



* Na3HP04 added after 50 minutes' shaking. See p. 106. 



t With N/10 HNO3 which removed 3-60 mgras. P2O5 per 100 gms. soil. See p. 108. 

 X With H2SO4 and then NaOH. See p. 94. 



^ Owing to the richness of this soil in phosphates it had to be subjected to a prehminary 

 extraction with N/5 nitric acid. 



Journ. of Agric. Sci. vni 6 



