1910.] 



PUBLIC DOCUMENT — No. 31. 



77 



THOMAS SLAG. A SHORT HISTORICAL 



REVIEW. 



BY J. B. LINDSEY. 



Thomas slag, or basic phosphatic slag, is a by-product in the 

 modern method of steel manufacture from ores containing notice- 

 able quantities of phosphorus. The process of removing the 

 l)hosphorus from the ore was discovered by the English en- 

 gineers Gilchrist and Thomas, and, briefly stated, consists in 

 addinc: to the so-called converter containing the molten ore a 

 definite quantity of freshly burnt lime, which, after a powerful 

 reaction, is found to be united with the phosphorus, and swims 

 upon the surface of the molten steel in the form of a slag. 



Composition^ of the Slag. 



The composition of the Thomas or Belgian slag varies accord- 

 ing to the character of the ore and the success of the process for 

 removing the impurities. The following figures show such vari- 

 ations:^ — 



More or less metallic iron is enclosed in the coarse slag which 

 is generally thoroughly removed from the ground material by 



the magnet. 



1 Agriciiltur Chemie von Aflo)f Mjiycr, II Band, 2te Abtl., 6 Autlage pp. 1.38, 139. 



