No. 6. DEPARTMENT OF AGRICULTURE. 839 



which was hard to handle, to dry aud prepare in a grod mechanical 

 condition, they w'ere denounced by many chemists as valueless for 

 fertilizing purposes. 



The chemists, in stating that this class of phosphates was value- 

 less for fertilizing purposes, evidently went a step too far, for they 

 should have said that they were not suitable for the manufacture 

 of superphosphates. It is a notable fact, which some chemists evi- 

 dently overlooked, that the phosphoric acid which is found naturally 

 in the soil exists largely in the form of iron aud alumina phos- 

 phates. 



While this class of phosphates are not adapted for making super- 

 phosphates and, consequently, are unpopular with the manufacturer 

 of chemical fertilizers, j'et it must be admitted, in the light of results 

 of numerous experiments, that they are valuable in the raw state, 

 if finely pulverized, as a direct fertilizer. 



The following analysis gives a fair idea of the composition of this 

 class of phosphates: 



Per cent. 



Moisture, 12.36 



W'ater of combination 4.13 



Phosphoric acid,* 30.22 



Lime, 4. 16 



Mag-nesia Trace. 



Oxide of iron, 7.04 



Alumina I 24.00 



Carbonic acid, I None. 



Sulphuric acid j None. 



Fluorine, | Trace. 



Insoluble matter, sand, etc., 18.09 



100.00 



♦Equal to 6*. 87 per cent, of tri-basic phosphate of lime. 



FLORIDA SOFT PHOSPHATES. 



This is probably the most important alumina and iron phosphate 

 to the States of the Atlantic ocean border at the present day, both 

 from an agricultural and commercial standpoint. There is consider- 

 able deposits of this class of rock in Florida. It is known as soft 

 phosphate because of the ease with which it is broken up and pul- 

 verized. As has been said, it is not well adapted for treatment 

 with acid for making soluble phosphates, as the alumina and iron 

 make a sticky mass w'hich is hard to dry and keep in a good me- 

 chanical condition. Hence, it has not been mined extensively or 

 had a large sale. Locally, this soft phosphate has had extensive 

 use in its natural condition. Its application has given good results 

 on sandy land, which '\ad been given heavy dressings of the native 



