536 



KEW YORE STATE MUSEUM 



Analysis of fire clay from Ohio 



SiO^ 



AlgOg ...... 



Fe203 



CaO 



MgO 



K2O 



NagO 



Ignition . . . . 



Total 



1 



Total 

 analysis 



Per cent 



73.21 

 14.56 

 4.Y9 

 .51 

 1.07 

 1.75 

 1.16 

 3.70 



100.75 



Insoluble 

 inHgSO 



Per cent 



55.38 



2.35 



.39 



.15 



.05 



1.71 



60.03 



Tke insoluble residue consists of quartz, feldspar, and perhaps 

 traces of silicate minerals approaching feldspar in composition. 

 In orthoclase (the common feldspar) the amount of silica is about 

 3.51 times that of alumina. Therefore, the alumina of the insolu- 

 ble portion multiplied by 3.51 gives the silica of the feldspar, 

 which, subtracted from the total silica of residue, leaves the silica 

 present as quart.z. Thus, in the column 2, above, we have: 



Silica 

 Per cent 



2.35x3.51 = 8.25 



Alumina 2.35 



Fluxes 2.20 



Per cent feldspar '. 12 . 80 



Subtracting this from the total insoluble residue; gives the 

 amount of quartz. 



As the clay substance, mica and ferric oxid are the soluble 

 portion of the clay, their total composition is obtained by s\ibtract- 



