5Y0 NEW YOKK STATE MUSEUM 



The relation of FegOg to CaO it will be seen is as 1 : 2, or 

 1 : 3j but the lime could probably be lower still, and yet be 

 effective. To prove this .Seger took the red burning clay from 

 Katbenow, wbose composition is 



Silica 61 .30 



Alumina - 18. 8Y 



Ferric oxid 6.66 



Lime , .85 



iMagnesia 1.20 



Alkalis 3.20 



Water 8.28 



To this clay be added increased amounts of lime, wbicb gave 

 the proportions of ferric oxid to lime carbonate in the different 

 mixtures, as follows : 



1:.13, 1:.48, 1:.83, 1:1.18, 1:1.53, 1:1.88, 1:2.23, 1:2.58, 

 1:2.93. 



These nine samples were first burned at a red heat in a small 

 gas furnace, and on cooling the color of all of them was found to 

 be red. 



They were next heated to bright redness and after this it was 

 found that the color of the first four was bright red, but still 

 slightly off color, the more so the greater the proportion of lime 

 which they contained. The fourth had a yellowish brown shell, 

 one millimeter thick with a red interior. The fifth and sixth 

 showed the yellow color to a greater depth, while the seventh and 

 eighth were yellow throughout with a slight tinge of gray. 



From this Soger infers that the yellow color first appears when 

 the proportion of ferric oxid to lime is as 1 to 1 



As regards the action of ferrous oxid. Soger came to the con- 

 clusion that in potous bricks the percentage of this can run quite 

 high without producing much effect, but in dense bricks the re- 

 verse is true. 



