^ LIME AND CEMEiS[T INDUSTBIES 667 



USES OF LIME 

 Basic steel 



In tte basic or Tliomas and Gilchrist process the furnace or bes- 

 semer converter is lined with some basic material (that is material 

 containing little or no silica), such as magnesite or dolomite. In 

 this country the latter specially is used. Two things are required 

 of the dolomite, viz, it should contain as high a percentage of 

 magnesia as possible, and it should not have over li^ or 2fo of 

 total fluxing impurities. It is specially important that the silica 

 percentage shall be low, viz, under ifo if possible, for at high 

 temperatures the lime or magnesia will eagerly unite with any 

 silica present, and, as this action is -equivalent to corrosion of 

 the lining, any additional percentage of silica will materially 

 affect the life of it. Pure dolomites are rare and when found 

 are not always in easily accessible localities, but in this state 

 two different bodies of nearly pure dolomite are known, the 

 one at Ossining and Tuckahoe, Westchester co., the other at 

 Rochester, Monroe co. 



For use the dolomite is first burned to the sintering point and 

 then ground and mixed with tar or other material to hold it 

 together and permit molding. 



The lime used in basic bessemer converters likewise has to be 

 of great purity, and the stone must be of such a nature that it 

 will burn to a lumpy and not a powdery lime; for, if the lime 

 were added to the converter in the form of pow^der, the strong 

 blast would quickly eject a large portion of it. 



Refractory bricks 



It is well known that oxid of lime is very refractory, a familiar 

 illustration of this fact being the lime pencils used in the oxy- 

 hydrogen blow pipe. Consequently lime is often used for lining 

 the bottom of the hearth in a reverberatory furnace used for the 

 manufacture of basic steel by the Siemens-Martin process. The 

 lime serves to extract the phosphorus from the iron, and a high 



