n 

 SLAG ANALYSIS 



DAILY WORK. Slag. — The composition of the slag in any 

 given smelting operation has probably a greater influence on the 

 success of the process than any other single factor, regarded either 

 from a technical or financial standpoint. 



Smelting may be regarded as the fusion or reduction of an ore 

 or ores, so that the resulting metal or matte, by reason of its 

 greater specific gravity, may sink through the fused gangue, and 

 be collected for further purification freed from the earthy metals 

 which form the slag. In order that this separation may be com- 

 plete and perfect, the slag must fuse at a temperature as near the 

 fusing point of the metal as possible, and in most cases, the more 

 fluid the slag, and the lower its specific gravity, the better it is. 

 In the lead, copper, and iron industry, the slags are invariably com- 

 plex silicates; that is, a silicate of numerous bases. The ratio of 

 acid to base has an exceedingly important influence on the perfect 

 separation of the metals from the slag, affecting, as it does, the 

 specific gravity, the fusibility, the influence on the furnace walls, 

 and the influence on the oxide of the metal to be separated. 



In general, it has been found that "singulo-silicates" are the 

 most fluid, fuse at the lowest temperature, and are most commonly 

 used where economically possible. (A slag in which the ratio of 

 the oxygen combined in the silica, is to the oxygen combined in the 

 bases, as 1 is to 1, is called a singulo-silicate.) 



It has been found that, if a slag be suddenly chilled, either by 

 pouring into water, or upon a cold piece of steel, or even by dip- 

 ping a cold steel bar into the fluid slag and quickly removing it 

 with its adherent slag, the slag so treated has a vitreous lustre 

 and decomposes rapidly and completely with acids. If, however, 

 it is allowed to cool slowly, as it would under ordinary circum- 

 stances, it is no longer decomposed by acids, but requires fusion 

 with alkaline carbonates. With singulo-silicates the decomposi- 



