316 CLAYS AND CLAY INDUSTRY. 



In this table the second to ninth columns inclusive represent 

 the determinations made in the ultimate analysis. A partial 

 analysis, only, of some of the samples was available, and in these 

 cases the difference between the sum of the substances determined 

 and ioo was taken as representing the sum of the lime, magnesia 

 and alkalies. The clay base given in the tenth column was ob- 

 tained by considering the alumina to be contained in kaolinite, 

 figuring the amount of silica necessary to unite with it, and adding 

 the combined water to it ; the total of the three then represents the 

 clay base. 1 The difference between the silica necessary to com- 

 bine with the alumina and form the clay base and the total silica, 

 was considered as representing the free silica. The twelfth column 

 represents the sum of the iron oxide, lime, magnesia and alkalies. 

 The last column gives the cone of fusion. 



Examining the percentages given we see that in the first an- 

 alysis the percentage of clay base is 87.20 per cent, and silica 

 10.65 P er cent., while the total fluxes are 0.78 per cent. Com- 

 paring these percentages with the curve (Fig. 41), we see that 

 a mixture of 90 per cent, kaolinite and 10 per cent, silica (IX), 

 which is close to the composition of clay No. 1 of the table, melted 

 at cone 34, so> that the 0.78 per cent, fluxes probably exert little 

 influence. 



Again in the third analysis, the percentage of clay base or 

 kaolinite is 52.82 per cent, and that of the silica 43.71 per cent.; 

 from the curve in Fig. 41 such a mixture would fuse at approxi- 

 mately cone 29. But we have here in addition to the silica. 2.13 

 per cent, total fluxes, so that we should expect the clay to fuse at 

 a still lower cone. By actual test the fusion point was found to> 

 be cone 27, so that evidently both the free silica and fluxes present 

 force down the fusing point and the facts correspond to the theory. 



No. 4 of the table of analyses behaves similarly to No. 3, and 

 No. 5 has a higii fusing point on account of its high percentage 

 of clay substance and low amount of fluxes. 



In the case of No. 6 we find that, leaving the fluxes out of 

 consideration, a mixture of kaolinite and silica in the proportions 



1 The amount of water present as an ingredient of limonite is so small in 

 these cases that it can be neglected. 



