FIRE CLAYS AND FIRE-BRICK INDUSTRY. 319 



present, 5 or 6 per cent, of titanium oxide colored the clay deep 

 blue on vitrification, but the addition of 5 per cent, silica in place of 

 some kaolin exerted a bleaching influence on the color. Not only 

 so, but, as shown by the curves, it reduced the fusion point. Thus, 

 No. VI ( Fig. 25) (kaolin 95, titanium oxide 5) fused just above 

 cone 32, whereas No. VIII (kaolin 90, silica 5, titanium oxide 5) 

 fused above cone 31, and a still further increase in the silica 

 lowered the fusing point still more. It seems evident, therefore, 

 not only that silica and titanium, oxide each act as a flux at high 

 temperatures when mixed with kaolin, but that their combined 

 action when both are present is greater than of either singly. 

 Since titanium acts so strongly, when present in small amounts, 

 it certainly seems necessary to determine it in the analysis of a 

 fire clay or fire brick. 



For purposes of comparison, and as further illustration of the 

 facts given above, some additional analyses are given of both 

 American and foreign clays. 



The analyses of the native clays are taken from a paper by 

 H. O. Hofman. 1 



Analyses of some American fire clays. 

























ri 











V 



























t, 















U) 







-d 



















3 



Locality. 





V 



a 









'en 















-• 



•2" 



1 





a 



a 





cd 



u 



V 





O 

 V 









• 3 



u 







•o 





3 



a 





cd 

 -x 







<! 



to 



►4 



£ 



Ph 







£ 



to 





 



Athens, Tex , . . 



37.06 



31.82 



20.71 



1 01 



0.22 



0.39 



69 



0.39 



7.17 



2.70 



29 



St. l,ouis. Mo.. . . 



38.32 . 



26.03 



21.16 



2.72 



0.61 



0.30 



0.86 



0.88 



8.94 



5 37 



30-31 



Golden, Colo., . . 



5-22 



7-13 



45-99 



31.72 



o-75 



0.36 



0.23 



0.48 



o-45 



13-30 



2.27 



31-32 



Mineral Point, O., 



1.68 TiO 2 

 3.10 



35-39 



31-84 



0.67 



0.50 



0.19 



0-59 





11.68 



i-95 



33 



Sayreville, N. J., . 



1.20 Ti0 2 



41.10 



38.66 



0.74 







0.28 



0.18 



13-55 



1.20 



35 







1 Trans. Amer. Inst. Min. Engrs. Vol. 24, p. 42, and Vol. 25, p. 3. 



