1<)1().1 rriiLId DOCUMENT — No. ;u. 77 



THOMAS SLAG. A SHORT HISTORICAL 

 REVIEW. 



BY J. B. LINDSEY. 



Thomas slag, or basic phospbatic 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 

 phosphorus from the ore was discovered by the English en- 

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

 adding to the so-called converter containing the molten ore a 

 definite quantity of freshly burnt lime, v^^hich, after a powerful 

 reaction, is found to l)e united with the phosj)horus, and swims 

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



CoMPOSITIOISr OF THE SlAG. 



The composition of the Thomas or Belgian slag varies accord- 

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

 removing the impurities. The following figures show such vari- 

 ations:^ ■ — ■ 



Per Cent. 



Phosphoric acid, ....... 11—23 



Silicic acid, ........ 3—13 



Calcium oxide (lime), . . . . . . 38—59 



Ferrous and ferric oxides, ..... 6—25 



Protoxide of manganese, 1^6 



Ahimina, 2—3.7 



Magnesia, 2-8 



Sulphur, 2-1.4 



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

 is generally thoroughly removed from the ground material by 

 the magnet. 



' Agricultur Chemic von Adolf Ma^vcr, 11 Band, 2tc Abtl., 6 AuHaKC pp. 138, 139. 



