SOURCES OF PHOSPHORIC ACID. Ill 



bones originally. In short, it would seem that the 

 United States are so abundantly supplied with the 

 most important of all plant foods, and for so long a 

 period, that we may be relieved of all anxiety for 

 the future concerning this material. With all these 

 mines in full working order, there is every reason 

 to believe that prices of this plant food will have a 

 downward rather than an upward tendency. 



The phosphatic guanos imported from some of the 



islands in South America, and supposed to be the 



droppings of sea fowls, with most of the nitrogen 



washed out by rain, contain from fifteen 



iSam°e*etc ^^ forty per cent of phosphoric acid, 

 and in some cases more or less nitrogen 

 and potash. Usually they are treated with sul- 

 phuric acid, and thus changed into superphosphate. 

 But with the abundant supply we have in our own 

 country, I fail to see why it should be necessary for 

 us to look to South America or any other country 

 for phosphoric acid. The same is true of apatite, 

 which is a phosphate rock of supposed purely min- 

 eral origin, found in Canada. If treated with sul- 

 phuric acid, and thus rendered soluble, apatite is 

 probably as useful as any other form of soluble 

 phosphoric acid; but the raw material is usually 

 considered of less value than South Carolina rock. 



A waste or by-product of the German and English 



iron industries, known as Thomas', or basic, slag, 



phosphate meal, etc., has frequently 



Basic Slag. ^^^^ mentioned in the press, and at 

 recent horticultural meetings, as a cheap source of 

 phosphoric acid. We used to get it from the New 

 York importer at thirteen to fifteen dollars per ton. 

 Now a firm in Pottstown, Pa., is manufacturing and 

 offering it as fertilizer under the name of " odorless 



