PROCESS OF MANUFACTURE IQ3 



these slags have been made in this country are Pottstown, Penn- 

 sylvania and Troy, New York. Comparatively small quantities 

 have been manufactured and the industry has not assumed any 

 commercial importance. In Europe they are extensively manu- 

 factured in England, France and Germany, and their use for 

 agricultural purposes has increased until it is quite equal to that 

 of superphosphates. 



The quantity of basic slag manufactured in Germany in 1893 

 was 750,000 tons; in England 160,000; in France 115,000, making 

 the total production of central Europe about 1,000,000, a quantity 

 sufficient to fertilize nearly 5,000,000 acres. During the year 

 1907 it is estimated that German agriculture made use of from 

 1,500,000 to 1,600,000 tons of basic phosphate slags. The total 

 output of basic slag is undoubtedly not far from 2,000,000 tons. 

 The total production of basic slag is therefore approximately 

 cne-half of that of crude phosphates. 



The following table in metric terms shows the estimated pro- 

 duction of crude phosphates for the whole world for 1906 and 

 1907 : 45 



1907 1906 



United States 1,917,000 2,052,000 



Tunis 1,040,000 758,000 



Algeria 325,000 302,000 



South Sea Islands 300,000 250,000 



France 375, ooo 425,000 



Belgium 180,000 155,000 



All other places 100,000 100,000 



4,237,000 4,042,000 



164. Process of Manufacture. The principle of the process 

 depends upon the arrangement of the furnaces, by means of 

 which the phosphoric acid in the iron ore or pig iron is caused to 

 combine with the lime, which is used as a flux in the converters 

 A general outline of the process is as follows : 



The pigs, which contain from two to four per cent, of phos- 

 phorus, are melted and introduced into a Bessemer converter lined 

 with dolomite powder cemented with coal-tar, into which has 

 previously been placed a certain quantity of freshly burned lime. 



45 Der Saaten-, Diinger-und Futtermarkt, 1908, No. 7 : 205. 

 7 



