152 



BASIC SLAG WOLTEES PHOSPHATE 



attempts have been abandoned, and the only process through which 

 the slag is passed is that of grinding. This must be thoroughly done, 

 for it is found that the availability of the phosphoric acid depends very 

 largely upon the fineness of subdivision. A sample should contain at 

 least 80 or 90 per cent of powder which passes through a sieve of 100 

 meshes to the linear inch, i.e., 10,000 to the square inch. Thomas' 

 phosphate has given excellent results, especially in soils somewhat de- 

 ficient in lime and rich in organic matter. 



The magnitude of the trade in basic slag may be gathered from 

 the accompanying table giving the quantity sold as a fertiliser in 

 Europe during 1899. 1 



So successful has Thomas' phosphate proved as a manure that 

 lately a product, known as "artificial Thomas phosphate meal," has 

 been made in Germany by a method devised by Wollers. Eaw 

 mineral phosphates are fused with silicious materials, e.g., sand or 

 glass, and chalk or limestone, and a product resembling basic slag is 

 thus obtained. In another preparation potash is introduced. Ac- 

 cording to analyses of the two products by Maercker 3 they contain 



According to Wagner 4 Welters' phosphate is now prepared by 

 fusing a mixture of crushed phosphorite (100 parts), sodium bisulphate 

 (70), calcium carbonate (20), sand (22), and coal (6 or 7 parts). The 

 melt is granulated by being poured into cold water and is there finely 

 ground. 97 per cent of the total phosphate present is soluble in weak 



Engineering and Mining Journal, 69, 648. Jour. Soe. Chem. Ind., 1900, 574. 



2 26, 000 tons were imported, chiefly from Germany. 



3 Jah. Agric. Chem., 1899, 129. 



4 Bied. Zentr., 1904, 301; Jour. Soc. Chem. Ind., 1904, 615. 



