70 CLAYS AND CLAY INDUSTRY. 



Seger and Cramer, of Berlin, made experiments to determine 

 the effect of this substance in clay. They took two samples of 

 Zettlitz kaolin (which contained 98.5 per cent, of kaolinite or 

 clay substance), and to these were added 6.5 per cent, and 

 13.3 per cent, of titanium oxide, respectively; both were then 

 heated to a temperature above the fusing point of iron, the result 

 being that the first softened considerably on heating and showed 

 a blue fracture, while the second fused to a deep-blue enamel. 

 A second series of mixtures, consisting each of one hundred 

 parts of kaolin, with 5 per cent, and 10 per cent, of silica, 

 respectively, showed no signs of fusion, and burned simply to a 

 hard white body, thus indicating that the titanium acts as a flux 

 at a lower temperature than quartz. 



As these experiments were not sufficiently extensive to be 

 applicable to New Jersey materials, which contain small but 

 persistent quantities of titanium, it was thought desirable to make 

 some mixtures of a white-burning refractory clay, with varying 

 percentages of titanium. The clay employed was a white-burn- 

 ing sedimentary clay from Columbia, South Carolina, the fusing 

 point of which is above that of cone 34. The titanium was added 

 in the form of rutile, which had been very finely ground in a 

 ball mill, most of it being fine enough to remain in suspension 

 for several days. 



Series of mixtures for tests on effect of Titanium oxide. 

 I. Clay plus y 2 % TiOs by weight. 



II. Clay 



' 1% " 



(( ( 



III. Clay 



' 2% " 



it . d 



IV. Clay 



' 3% " 



a a 



V. Clay 



' 4% " 



a a 



VI. Clay 



' 5% " 



a a 



These mixtures were then formed into small cones and tested 

 in the Deville furnace, the results of these tests being shown 

 graphically by the curve in Fig. 25. In this figure the vertical 

 line at the left represents the cone number of the Seger series, 1 

 and the horizontal line at the bottom the per cent, of titanium 



1 See Fusibility, Chapter IV. 



