144 



PHOSPHATES SUPERPHOSPHATES 



The extent and growth of the phosphate mining industry may be 

 seen from the following table, giving the total production, in tons, of 

 raw phosphates in 1880 and 1890 : l 



Since 1890 many new sources of phosphates have been discovered 

 and the total production has greatly increased. The Florida deposits 

 alone, in 1903, yielded 860,000 tons, while the total production of the 

 United States was estimated at 1,581,000 tons. Large quantities also 

 come from North Africa (chiefly Algeria) : in 1903 this district yielded 

 647,846 tons. 



The following table gives the average composition of a number of 

 mineral phosphates : 



Redonda Phosphate (Leeward Islands) consists largely of alum- 

 inium phosphate and is therefore, in its raw state, not of much value. 

 Lahn phosphate also contains a considerable quantity of ferric oxide 

 and alumina, which lowers its value. 



Mineral Superphosphates. It is for the manufacture of these 

 substances that the mineral phosphates are chiefly used, for in their 

 raw state the latter are too insoluble to be of much value as fertilisers. 

 In an extremely fine state of division, however, they become more 

 available and are sometimes used. 



. No. 15, U.S. Dept. of Agric., 1893. 



