An investigation of the silica deposits of southern Illinois . tures are made up of the forms of silica, stable at high temperatures, isthe factor that makes silica a valuable refractory. The fact that silica minerals change their form at various temperaturesand that this change proceeds mare rapidly and v/ith different effects on thestrength of the material in various quartzites and cherts, causes many of theseto be eliminated from use for refractory purposes. The expansion (that is dueto inversion) should be eliminated as far as possible in the initial bum. Thisnecessitates that the material
An investigation of the silica deposits of southern Illinois . tures are made up of the forms of silica, stable at high temperatures, isthe factor that makes silica a valuable refractory. The fact that silica minerals change their form at various temperaturesand that this change proceeds mare rapidly and v/ith different effects on thestrength of the material in various quartzites and cherts, causes many of theseto be eliminated from use for refractory purposes. The expansion (that is dueto inversion) should be eliminated as far as possible in the initial bum. Thisnecessitates that the material decreases in specific gravity considerably duringthe first bum and but little in subsequent bums. The table below designates^,(a) good material, (B) fair material, and (C) p®or, v/here the burning was doneat Cone 15-16. ^ S. Tech. Paper 116 - Page Silica Refractories. 2lddingB - Rock Minerals - Page 544 - 5. Tech. Paper 116 - Page 5. QuairbzChert or ^ ChalcedonyCristobaliteTridymite Rate of 5. A B C Before Heating After let Heating Cone 15-16 After 3rd Heating Cone 15-16 After 5th Heating Cone 15-16 As seen from the table, (A) practically completes its drop in specificgravity in one bum, while (C) continues to drop after five burns. A matei*iallike (C) consists usually of a pure coarse grained type and usually cracks andweakens materially during the heating. This, of course, woxild weaken the wareand make it unfit for use. The effect of the addition of various agents that can be used in bondingthe silica material and of others which may come in contact with the materialhas been studied and various results have been obtained. Ross^ found thatTennessee Ball Clay, AI2O3, CaF2» and Fe203 did not seem to increase the rateof inversion. He found, however, that the addition of NaCl and the increasingof the lime content did to a marked degree. Shale with lim
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Keywords: ., bookcentury1900, bookdecade1920, booksubjectminesandmineralresou
