New York Agricultural Experiment Station, 285 



mined by the Neumann method. The reagents used were phos- 

 phorus free. 



Below we give the results in percentages of air-dried material. 



Table V.— Separation of Forms of Phosphorus with Tannin and 

 Sodium Acetate. 



These results give further evidence that tannin and sodium 

 acetate could not be used for the separation of organic and inor- 

 ganic phosphorus in such materials. 



METHOD ADOPTED. ^' 



The method we have finally adopted as giving results nearest 

 the truth is that detailed above for the hydrochloric-acid extract 

 of Table IV, with the following modification. After ignition the 

 magnesium pyrophosphate is dissolved in dilute nitric acid and 

 the phosphorus reestimated. This, as detailed above, is to pre- 

 vent the error of weighing magnesium pyrophosphate contami- 

 nated with magnesium oxide. We do not expect the method in 

 all cases to give absolute results. What we claim for it is that 

 it reduces the hydrolyzing action of the reagents to a minimum, 



