138 ANNUAL. HKPORT OF THE Oft. boc. 



Pennsylvania. The phosphoric acid is present as tetra-calcium phos- 

 phate and is insoluble in water and only partially soluble in ammonia 

 citrate. When applied to the soil, however,, it seems to have a fav- 

 orable effect and is used, especially in Germany, to quite an extent 

 as a fertilizer. It has not been used to a great extent in this country, 

 but in many instances has shown good results. The ordinary 

 methods of fertilizer analysis show it to contain from 15 to 20 per 

 cent, of phosphoric acid, 5 or 6 of which are soluble in ammonia 

 citrate. 



Phosphate Roch : The deposits of phosphate of lime found in South 

 Carolina, Florida and Tennessee, are the chief sources of phosphates 

 for fertilizer manufacturing purposes. South Carolina phosphate 

 v*'as discovered in 1844, but the first artificial fertilizing material was 

 not prepared from this source until about 1868. These phosphates 

 occur or are known under two separate heads, as Land Rock and 

 River Rock, depending upon the location in which they are found. 

 They vary somewhat in their physical properties, but their chemical 

 composition is about the same. The laud rock is somewhat lighter in 

 color — yellow or gray — and occur in nodules. These nodules are 

 easily broken, and ground to a fine powder, they constitute so-called 

 "floats." While the term, rock, is applied to them and while they 

 resemble rock in most particulars, they are the result of deposits of 

 land and marine animals. South Carolina rock contains from 25 to 



28 per cent, of phosphoric acid. 



Florida Phosphate: These deposits were discovered in 1881; but 

 it was not until 1888^, that their presence was generally known and 

 that shipments were made from this field. The composition of the 

 Florida i)hosphates is not greatly different from those of South Caro- 

 lina. They contain more iron and alumina'phosphate, and run smal- 

 ler in size, hence they are often designated as pebble phosphate. 

 There are both land and river deposits of these pebble phosphates 

 as well as land rock deposits. 



Tennessee Phosphate: In 1894, phosphate deposits were discovered 

 in Tennessee, and these are being used to a considerable extent to- 

 day. In case of these deposits, they are not found in pebble, nodule 

 or boulder form as in South Carolina and Florida, but occur in veins 

 and pockets. Their composition is also somewhat variable. 



Apatite is a form of phosphate of lime found in New York State 

 and in Canada. From the fact, however, that it is very hard and, 

 therefore, difficult to grind; it is not used for manufacturing pur- 

 poses except to a very limited extent. It sometimes contains as 

 high as 40 per cent, of phosphoric acid. 



Coprolites and Phosphorites, sometimes spoken of as sources of 

 phosphoric acid, are found in Europe, but are not used in this coun- 

 try. 



