heat so long as the water of hydration and the organic 

 matter still remained in the soil ; therefore no additional 

 surface would be exposed to the action of the acid 

 and besides, the dehydration of the organic, as well 

 as inorganic phosphates, would seem to make them 

 less soluble. Indeed I have -data to show that de- 

 hydration without ignition also decreases the solu- 

 bility of the soil phosphates. This explanation is 

 offered by the writer for the facts noted, merely as a 

 suggestion as to the pheno'mena probably occurring 

 when mineral phosphates and soils are heated, as re- 

 gards their phosphate content. It is hoped that an 

 explanation or further suggestions will be forthcoming 

 from my colleagues. This brief paper is offered merely 

 as a partial report on one phase of the subject of the 

 determination of phosphoric acid in soils, the whole 

 of which is now being studied in our laboratory. Other 

 interesting data besides that mentioned has already 

 been obtained which we hope to include in another 

 paper in which the whole subject will be treated more 

 completely. 



SOILS RESEARCH LABORATORY, 

 UNIVERSITY OF CALIFORNIA, BERKELEY. 



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