192 Indiana University Studies 



proper composition to form a good grade of cement, 11 

 properly handled. When the slag is to be used as material for the 

 manufacture of cement it is drawn off into water where it takes on 

 a coarse granular texture which leaves it in an easily handled 

 form. Great efforts are made to maintain the proper quality 

 of the slag, and if a uniform grade of iron is to result the composi- 

 tion of the slag must be carefully watched. 



Both limestone and dolomite are extensivley used for fluxes 

 thruout the country. Both of these fluxes have their advantages, 

 but as the manufacture of cement from blast f irnace slags becomes 

 more widespread the demand for a high ca lum limestone will 

 increase for the reason that the slags from dolomite flux are not 

 suitable for the manufacture of cement. 



The slags obtained from high calcium fluxes develop hydraulic 

 properties when allowed to cool quickly. This is accomplished 

 by running the molten slag into water. The resulting granular 

 product is dried and ground very fine, and mixed with a certain 

 percentage of slaked lime, and this mixture is again ground so 

 as to pass a 200-mesh sieve. The resulting powder will have the 

 properties of a good hydraulic cement. This form of cement 

 works best in places where it is constantly wet, because drying 

 tends to disintegrate it. 



Dolomite flux is favored in the Birmingham iron district, 

 as shown from the following quotation from the work of Burchard- 

 Butts and Eckel on ''Iron Ores, Fuels and Fluxes of the Birming- 

 ham District, Alabama" {Bulletin No. 400, U. S. Geological 

 Survey, p. 197) : 



The fluxing power of dolomite is greater than that of limestone; an 

 equivalent of carbonate of magnesia weighs 84, while an equivalent of car- 

 bonate of lime weighs 100; in fluxing power these equivalents are equal 

 because the power of a base to combine with an acid does not depend upon 

 its atomic weight, but upon its chemical affinity. So the fluxing powers 

 of the two carbonates are to each other as 84 to 100. 



The dolomite of this district is a great deal purer than the limestone. 

 The foreign matter of the former does not exceed 2 per cent while of the 

 latter an average is at least 4 per cent. To determine the value of a stone 

 as a flux we must deduct the impurities it contains, plus as much of the base 

 as is necessary to flux those impurities. Taking the limestone as a 96 per 

 cent lime carbonate, and deducting 8 per cent to take care of its own im- 

 purities, we have left 88 per cent of lime carbonate as available flux. Taking 

 the dolomite to contain 2 per cent of impurities and 43 per cent carbonate 

 of magnesia, with 55 per cent of carbonate of lime, we have left, after deduct- 

 ing 4 per cent of the carbonate of lime to take care of the impurities, 43 per 

 cent of magnesia carbonate and 51 per cent lime carbonate. The fluxing 



