106 Dilute Acids and Phosphorus Compounds in the Soil 



The change of adsorption with the time. 



Reverting to Figs. 4 and 5, it is clear that adsorption in presence 

 of nitric acid becomes more pronounced as the length of the action 

 proceeds. Three times were studied : Time = 0, 1 hour, and 24 hours. 

 The adsorption successively increases, and has become very marked 

 after 24 hours. 



Agdell Soil. 



60 



20 Q 30 40 



PjOg mgm. per 1000 c.c. of solution 

 Fig. 9. Effect of composition of the solution on adsorption phenomena. 



The first explanation that occurs is that adsorption is a slow business 

 and takes a long while to complete itself. Some support is given to 

 this view by the following experiment: 



One lot of soil was shaken for an hour with N/10 nitric acid and 

 sodium phosphate in the usual way. Another lot was shaken with 

 the acid for only 50 minutes, then the phosphate was added and the 



