24 The Phosphates of America. 



It appears to be established by the record of this congress that 

 French and German agricultural chemists are now in accord in re- 

 gard to the comparative value of soluble and precipitated phos- 

 phates (i.e., those which had once been soluble but have returned 

 to the insoluble state in fine division), French chemists having 

 held for some time that they should be on an equal footing. They 

 also assented to the value of raw ground phosphate of lime, and 

 declared that 



" The congress is of opinion that in reports of analyses the 

 directors of stations should state the solubility of phosphates by 

 the expressions ' phosphoric acid soluble in cold citrate of ammonia ' 

 or * soluble in water,' and not that of f assimilable phosphoric acid ; ' 

 the Congress believing that to apply the term assimilable to the 

 phosphate soluble in the citrate would be to class implicitly and 

 necessarily in the category of substances not assimilable, the phos- 

 phates which are evidently soluble in the soil, such as those in 

 bone ash, guano, bone powder, farm-yard manure and fossil phos- 

 phates." 



There is probably not a single one of our agricultural experi- 

 ment stations in which the assimilability of raw mineral phos- 

 phates finely ground has not been the object of intelligent study, 

 but so far as we have been able to ascertain by diligent inquiry up 

 to date, the results have varied, as we have already premised, in 

 accordance with the kind of phosphate used and the nature of the 

 soil into which they were introduced. Nothing of any serious mo- 

 ment has in fact occurred to modify the conclusions formulated in 

 1857 by the well-known Frenchman, De Molon, who, reporting on 

 a very extensive series of trials of ground raw coprolite in many 

 different departments of France, said that 



1. It might be used with advantage in clayey, schistous, grani- 

 tic and sandy soils rich in organic matter. 



2. If these soils were deficient in organic matter or had long 

 been under cultivation, it might still be used in combination with 

 animal manure. 



3. It may not be used with advantage in chalky or limestone 

 soils. 



Here, as it strikes us, is a fairly representative case where an 

 intelligent discrimination is demanded of the farmer, and where he 

 must realize that the term soluble as applied to phosphate fertilizers 

 is an entirely relative one. In one portion of his lands he may use 

 raw phosphates, and they will prove to be soluble and produce 



