440 CLAYS AND CLAY INDUSTRY. 



It showed many small cracks at cone 3, and burned steel-hard 

 at cone 5. 



When tested in the Deville furnace at cone 27 it was not beyond 

 incipient fusion, and fused above cone 34. It is, therefore, a very 

 refractory clay, but owing to its cracking, cannot be used alone. 

 It has the following chemical composition : 



Chemical analysis of No.i fire clay. M. D. Valentine & Bros. Co., Woodbridge. 



Raw. Burned} 



Silica (SiOs), 50.60 57.93 



Alumina (A1 2 3 ), 34.35 39.33 



Ferric oxide (Fe 2 3 ), 0.78 0.89 



Titanium oxide (TiO=), 1.62 1.85 



Lime (CaO), tr .... 



Magnesia (MgO), tr 



Loss on ignition (chiefly water), 12.90 .... 



100.25 



This clay is low in fluxing impurities and moderately low in 

 silica, so that from the analysis alone its refractoriness is ap- 

 parent. In order to show the percentages that would appear in 

 the burned clay, the re-calculated analysis with the water omitted 

 is given in the second column. 



No. 1 fire clay, Anness & Potter. 2 A second sample of No. 1 

 fire clay, from the pit of Anness & Potter (Loc. 6), resembled the 

 preceding in its properties. It is a soft, grayish-white clay (Lab. 

 No. 373), of irregular fracture and medium porosity, slaking 

 slowly in water. The water necessary to work it up was 33 per 

 cent., and gave a plastic mass averaging 41 pounds per square 

 inch in tensile strength. The air shrinkage was 5 per cent. In 

 burning the material behaved as follows : 



Burning tests of No. 1 fire clay. Anness & Potter, Woodbridge. 



Cone 5 8 



Fire shrinkage, 7.5% 11% 



Absorption, 13-74% 9.10% 



Color, cream-white cream 



1 This column gives the analysis re-calculated to 100 per cent., with the water 

 left out, and shows the percentages as they would be after the clay is burned. 

 ' No. 5 of section on page 455. 



