160 JoUPt:N"AL OF THE MlTCHELL SoCIETY [Mavch 



siderably lower wattage per candle-power than is now required by the 

 average metal filament lamp. Analysis of one such alloy shows zir- 

 conium, 65 per cent; iron, 26 per cent; titanium, 0.12 per cent; and 

 aluminum, 7.7 per cent. These alloys are produced by reduction 

 with finely divided aluminum together wdth the mixed oxides of iron, 

 titanium, or whatever metal it is desired to introduce with the alloy. 

 Or they may be produced by heating the mixed oxides in a graphite 

 crucible in an electric furnace using either zircon or zirk elite as a 

 source of zirconium. 



For use as a scavenger in casting steel a 20 per cent ferro-zirconium 

 is recommended in an amount equal to 1 per cent of the weight of 

 steel treated. 



Mixed with good conductors zirconia is said to 



FURNACE . ° 



ELECTRODES improve furnace electrodes. On account of its low 



conductivity for both heat and electricity it can 

 also serve as an insulating material. It is further used to replace 

 thorium nitrate for coating the iridium bar and preventing the loss of 

 iridium in the Heraeus furnace. 



The oxide, zirconia, possesses physical and chemical j^roperties 

 which make it available for a variety of industrial uses. Among these 

 properties are its high melting point and its low heat conductivity. 

 On account of its low coefficient of expansion it withstands sudden 

 changes of temperature. Its porosity is low so that it is practically 

 impervious to liquids. It is inactive toward most chemicals and 

 scarcely attacked by strong acids or alkaline fusion mixtures. It does 

 not, however, resist the action of hydrofluoric acid and fluorides. 

 Fused bisulphates also act upon it to some extent. It is therefore 

 quite stable in the presence of most fluxes and slags. 



As binding material various organic substances, as starch, organic 

 acids, glycerin, tar, etc., have been recommended; also magnesia, 

 phosphates, and borates. Since the native zirconia from Brazil is 

 reasonably pure, it may be used direct with no other than mechanical 

 treatment. Xative zirconia begins to fuse at 1,800° C. Foi; use 

 in laboratories and chemical manufacture it is first purified. The 

 chief imjDurities to be removed are iron, titanium, and silicon. 



