110 Dilute Acids and Phosphorus Convpounds in the Soil 



obtainable by the crop. In no case do they stand for anything actual, 

 but only for a difference between a direct action and an adsorption which 

 varies with the nature of the acid and the conditions of the experiment. 



So long as they are confined to the same type of soil, however, any 

 of the acids investigated would have given useful results, but difficulties 

 would arise directly an attempt was made to compare dissimilar soils. 

 The proper way to use a soil analysis is in conjunction with a soil survey. 



A diffusion method is described in which the reverse reaction is 

 eliminated, and which therefore gives a true measure of the direct 

 action. But until we have had more experience with it we are not 

 prepared to say what value it has for soil analysis. 



{Received Ajnil ilh, 1916.) 



