CHAPTER XIX. 



THE ANALYSIS OF VIRGIN SOILS BY EXTRACTION WITH 



STRONG ACIDS. 



As stated already, the analysis of soils by extraction with 

 strong acids is intended to enlighten us, not in regard to their 

 immediate productiveness (the " Diingerzustand " of German 

 agricultural chemists), but as to their permanent value or pro- 

 ductive capacity. As has been seen in the preceding chapter, 

 the efforts to unite investigators upon a generally applicable 

 and acceptable method for the testing of immediate produc- 

 tiveness have not been very successful, and the number of 

 methods employed in different countries and by different 

 chemists within the same country are widely at variance, with 

 no immediate prospect of agreement. Moreover, in most 

 cases the effort is to combine both problems temporary and 

 permanent productive capacity in one method or operation; 

 which still farther confuses the issue. 



Convinced that the only way to unification lies in the direc- 

 tion of falling back upon a method that is based upon a natural 

 limitation about which there can be no difference of opinion, 

 the writer has, in following the lead of Owen and Robert 

 Peter, endeavored to settle definitely tlie natural limit of the 

 action of a suitable acid upon soils, and the time and strength 

 of acid producing the maximum effect. 



Loughridge's Investigation. Systematic work on these 

 points was undertaken, at his suggestion, by Dr. R. H. Lough- 

 ridge in 1871 and 1872. The results of this work were pub- 

 lished in the succeeding year in the Amer. Journal of Science, 

 and in the proceedings of the A. A. A. S. for 1873. They seem 

 to be of sufficient general interest to be reproduced here. 



The soil selected for this purpose was a very generalized one, 

 representing large areas in the states of Kentucky, Tennessee, 

 Mississippi and Louisiana, bordering on the east the immediate 



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