CHEMICAL PROPERTIES OE CLAY. 



5i 



crack in burning, and may also show high shrinkage. If 

 kaolinite is the only mineral present containing chemically com- 

 bined water, the percentage of the latter will be approximately 

 one-third that of the percentage of alumina, but if the clay con- 

 tains much limonite or hydrous silica the percentage of chemi- 

 cally combined water may be much higher. 1 



5. Excess of silica. A large excess of silica indicates a sandy 

 clay. If present in the analysis of a fire clay, it indicates low 

 refractoriness. 



6. The quantity of organic matter. If this is determined 

 separately, and it is present to the extent of several per cent., it 

 would require slow burning if the clay was dense. 



7. The presence of several per cent, of both lime (CaO) and 

 carbon dioxide (C0 2 ) in the clay indicates that it is quite cal- 

 careous. 



These are the main points determinable from the ultimate 

 analvsis. 



Analyses of several different types of clay: 



Silica (Si0 2 ), 46.3 



Alumina ( A1 2 3 ) , 39.8 



Ferric oxide (Fe 2 3 ), 



Lime (CaO), 



Magnesia (MgO), 



Potash (K 2 0), ,... 



Soda (Na 2 0), 



Water (H 2 0), 13-9 



Sulphur trioxide (S0 3 ),. . . 



Loss on ignition, 



Titanium Oxide (Ti0 2 ),... 



Moisture, 



Carbon dioxide (C0 2 ), ... 



2 



46.II 



39-55 



0-35 



O.I3 



1378 

 0.07 



3 



61.6 



28.38 



0.52 



0.46 



0.36 



5.08 

 3.6o 



4 

 56.10 

 27.42 



0.18 



} 2.71 



6.00 



1. 00 

 2.90 



5 



60.18 



23.23 



3-27 



1. 00 



.67 



2.58 



It] 



6 



46.55 

 12.66 



4.92 

 14.02 



4.67 



2.05 



. under C0 2 



•54 



100.27 



14.92 



99-79 



i. Kaolinite. 



2. Ball clay, Edgar, Florida. 



3. Fire clay, Woodbridge, N. J., W. B. Dixon Est. 



4. A buff-burning clay, Sayreville, N. J. 



1 See analysis of yellow clay from Tilton's yard, Toms River (Loc. 206), 

 Chapter XIX, Ocean County. 



