v.] 



SOLUBILITY OF PHOSPHATES 



145 



The kind of information which is yielded by the 

 attack of dilute solvents may be seen in Table XXXVII I., 

 which shows some of the results obtained by J. K. S. 

 Dixon when certain phosphates of similar character 

 were shaken with a 2 per cent, solution of citric acid. 

 The results agree in the main with practical experience 

 and with the field trials which have been made upon 



Table XXXVIII. — Relative Solubility of various 

 PHOsrHATic Manures (Dixon). 



these materials ; the phosphoric acid of bone meal is less 

 soluble than that of steamed bone flour, and the Indian 

 bones which have long been dried and exposed show a 

 lower solubility than do the fresh English bones. The 

 phosphatic guano and the steamed bone flour show 

 much the same solubility of their phosphoric acid, but 

 the younger the guano is, as indicated by the increased 

 percentage of nitrogen, the greater is the solubility of 

 the contained phosphoric acid. It will be explained 

 later that as the guano ages and loses its nitrogen the 

 phosphates pass more and more into tri-calcium phos- 

 phate, and eventually by solution and redeposition 

 become much the same material as a rock phosphate. 

 But while it would thus be possible by the use of one 



K 



