Metal shathed carbon electrode

Claim 1

IN A BAKED CARBON ANODE ADAPTED FOR USE IN AN ELECTROLYTIC CELL FOR THE PRODUCTION OF ALUMINUM FROM ALUMINA DISSOLVED IN A MOLTEN ELECROLYTE AND HAVING OVER ITS BONNET AND UPPER SIDE SURFACES, A SUBSTANTIALLY AIRTIGHT SHEATH COMPRISED OF ALUMINUM FOIL 0.001 TO 0.006 INCH IN THICKNESS, BONDED TO THE AFORESAID SURFACES BY AN ADHESIVE, THE IMPROVEMENT IN SAID ANODE WHICH CONSISTS IN SAID ALUMINUM FOIL SHEATH BEING TIGHTLY AND INTIMATELY BONDED TO SAID BAKED CARBON ANODE SURFACES BY A MASTIC COMPOSITION CONSISTING ESSENTIALLY OF ABOUT 40 TO 50 PERCENT BY WEIGHT BITUMINOUS MATERIAL HAVING A SOFTENING POINT LESS THAN ABOUT 110*C. AND SELECTED FROM THE GROUP CONSISTING OF TAR, PITCH AND MIXTURES THEREOF, AND ABOUT 60 TO 50 PERCENT BY WEIGHT AGGREGATE SELECTED FROM THE GROUP CONSISTING OF LOW VOLATILE COAL, COKE AND MIXTURES THEREOF, THE BULK OF WHICH PASSES A 100 MESH SCREEN AND SUBSTANTIALLY ALL OF WHICH PASSES A 28 MESH SCREEN (TYLER SCALE), SAID COMPOSITION BEING PRESENT IN AN AMOUNT OF ABOUT 0.3 TO 1.0 GRAM PER SQUARE INCH OF SAID SHEATHED SURFACES, SAID ANODE BEING CHARACTERIZED IN USE BY BEING SO PROTECTED BY SAID SHEATH AGAINST AIR BURNING AS TO OBVIATE THE NEED FOR THE CONVENTIONAL ALUMINA BLANKET OVER ITS UPPER SIDE SURFACES, WITHOUT INTRODUCTION INTO THE CELL OF MATERIALS CONTAMINATING THE ALUMINUM PRODUCED.