0)1 Tribasic Phosphoric Acid. L93 



(7) P0 6 35.64 Fusing Method (MO,) 

 Fe a 3 34.29 

 HO 30.07 



(8) P0 5 35.47 

 Fe a 3 35.23 

 HO 20.45 



a u 



As this finishes ray actual work, as regards the separation 

 of phosphoric acid from iron, I may be allowed to give my 

 views as to the state in which this acid occurs in iron ores, and 

 to call attention to some points which may finally lead us to suc- 

 ceed in preventing it from entering to a larger extent into the 

 composition of metallic iron. 



Phosphorus is always contained in iron ores as phosphoric 

 acid. I believe this to be the case even in bog ores, the only 

 ores in connection with which we might question this state- 

 ment. 



The oxides, and principally the sesquioxides of iron, have a 

 great affinity for phosphoric acid, and will retain it with a 

 strong force. The snbstances, however, accompanying iron 

 ores, as alkalies, alkaline earths, and alumina, have a still great- 

 er affinity for phosphoric acid than even sesquioxide of iron, 

 and will have taken up in the process of formation of iron 

 ore beds, either by a dry or a wet process, moal of the 

 phosphoric acid, so that the iron ore proper, it being consider- 

 ed as a mixture of pure compound of iron with some gangue, 

 or as the Germans term it, " Begleiter" will only contain a 

 very small amount of it. This amount of phosphoric acid, 

 which is necessarily contained in iron ores, is less in the mag- 

 netic than in the hematite varieties, inasmuch :i> the Btroug 

 combining powerof the sesqnioxide in the former ha- been 

 isfied to some extent by the protoxide present, mid we are 

 therefore able to obtain, under similar conditions, a better iron 

 from those than we can from hematites. This slight amount 



