146 Probable Error of SanipiiiKj in Soil Surveys 



determination of the total Po^s- T" ^lie case of the PoO^ determinations 

 it was felt tliat the error of analysis would be smaller if absolute deter- 

 minations were made. Accordingly, the total P2O5 was determined by 

 treatment with sodium peroxide. 



Fig. 1. Field A. 



In order to get some idea of the reliability of the figures obtained, 

 i.e. to determine p^ , six mechanical analyses and P2O5 determinations 

 were made of a well mixed composite sample of a number of borings. 

 The results are shown in the following table. 



Composite Sample. 



