178 



THE ROYAL SOCIETY OF CANADA 



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20r 



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Fig. 3. Rate of Reduction of Hematite and Magnetite at various temperatures. 



During the reduction the grains of ore become larger and acquire 

 a characteristic gray colour. Fig. 4 contains photographs, all with 

 the same magnification, showing, on the left, grains of hematite ore 

 in their original condition ; in the middle the same ore in the reduced 

 or metallized condition after treatment at 800°C., and on the right a 

 peculiar product obtained on one occasion at 850°C., in which the 

 grains had become coherent and had formed a light spongy mass. 

 It seems curious that the removal of oxygen from an ore should cause 

 an increase of bulk and a careful microscopic investigation of this 

 phenomenon might yield interesting results. 



In these experiments the ores were crushed to a uniform size of 

 between 30 and 40 meshes to the linear inch. Earlier work in this 

 laboratory had shown that when the ore was coarser than this the 

 rate of reduction was materially slower, and it was found that the 

 rate was not materially increased when the ore was more finely 

 crushed, apparently because of the poorer contact between the gas 

 and the individual grains of the ore. For magnetite ores, which are 

 slowly reduced in grains of this size, experiments should be made on 

 the effect of finer crushing combined with mechanical agitation of the 

 ore in the gas. 



In these experiments the ore was spread as thinly as possible 

 in the boat so as to obtain ample contact with the gas. The contact 



