172 AGRICULTURAL EXPERIMENT STATION. [Jan. 

 Ground Rock Phosphate. 



[Sent on from West Springfield, Mass.] 



Per cent. 



Moisture at 100° C, 0.10 



Total phosphoric acid, 30.51 



Soluble phosphoric acid, None. 



Reverted phosphoric acid, 0.19 



Insoluble iDhosi^horic acid (2 cents per pound), . . . 30.31 



Magnesium oxide, 3.03 



Calcium oxide, 41.87 



Ferric and aluminum oxides, 4.26 



Insoluble siliceous matter, 13.74 



The material is of but little value for manurial purposes, 

 without a previous treatment with sulphuric acid, to render 

 its phosphoric acid available. 



South Carolina Rock Phosphate. 



[Sent on from Asbby, Mass.] 



Per cent. 



Moisture at 100° C, 1.68 



Total phosiDhoric acid, " . . . 25.81 



Soluble phosijhoric acid, 0.27 



Reverted phosphoric acid, 0.47 



Insoluble phosphoric acid, 25.07 



Insoluble matter, 11.64 



The material is of fair composition, and ought to be manu- 

 factured into superphosphate before used. 



Natural Phosphate. 



[Sent on from New York.] 



Per cent. 



Moisture at 100° C, 3.26 



Total phosphoric acid, 28.95 



Reverted phosphoric acid, 1.50 



Insoluble phosphoric acid, 27.45 



Alumina and feme oxides, 11.76 



Calciiun oxide, 35.40 



The article is characterized by the presence of a liberd 

 amount of sesquioxide of iron and alumina. Actual field ex- 

 periments have to decide its agricultural value. 



