Demonstration of Combustion by Catalysis LEON McCULLOCH Westinghouse Research Laboratories, Eost Pittsbrcrgh, Penmsyluania
OMBUSTION by catalysis can be exhibited very Caprettily by use of acetone and metallic copper within an open beaker. No platinum is needed and no arrangement of tubes to pass alcohol vapor through a copper catalyst. The beaker may be about 500 ml. in size, containing acetone to a depth of 2 cm. a t room temperature. A ~iece'ofthick copper wire or of copper strip is hung by a hook:from a rod across the top of the beaker, having its
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lower end just above the surface of the acetone as shown. To start the combustion, the copper is lifted from the beaker and is preheated to redness by holding i t in the flame of a nearby Bunsen burner. While stiU red-hot, the copper is suddenly placed in position above the acetone. At contact with the vapor, the oxidized surface of the copper is reduced, and catalytic combustion commences. The copper remains at red heat and brightly metallic, except for the transient flow of oxide films across its surface as the result of convection currents. The movement of these oxide films resembles that of a flickering flame. To cut down the draft of heated air, the top of the beaker can he nartlv covered hv s t r i ~ of s cardboard or glass. The color effects are more striking when viewed in the dark. The combustion may continue until the acetone is all used up. Among the products of the combustion are aldehydes, as is strongly evidenced by their odor. A test with litmus shows acid also to be present. On account of the irritating nature of the vapors, the experiment should preferably he made with good ventilation. It seems remarkable that the acetone does not enflame or "catch fire." This is perhaps because of the unusuauy high ignition temperature of acetone. The experiment seems quite safe with reasonable precautions against accidents. &
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