Bill Aycock on wed 18 dec 96
At 09:45 AM 12/17/96 EST, you wrote:
>----------------------------Original message----------------------------
>Alumina oxide is white
>Non! Alumina oxide is reddish brown.
>Hold! Alumina oxide is black.
>
>So what color is it?
>
Jeff- actually, there are two different chrystal forms of the stuff--
regular old, common, Aluminum Oxide is "colorless", is a hexagonal chrystal,
and is the coating you see when you look at a piece of Aluminum. When a
chemist says "colorless" what he means is in the solid, layered form, as is
usually the case on metal. When you and I see this as a powder, we would
call it white.
The other common form is Corundum, which is white, and is a trigonal chrystal.
Aluminum, the metal, corodes so fast that the only way to see the metal
color, rather than the Oxide, is to scrubb it in oil or some other protector
that keeps the air from the surface. When you do this, you can get a black
appearance, because the small specks of metal will look black untill they
get to the air.
The red color- I dunno unless it is rust, which is a great abrasive, in its
own right.
Bill- feeling kind of rusty himself, on Persimmon Hill
Bill Aycock --- Persimmon Hill --- Woodville, Alabama, USA
--- (in the N.E. corner of the State)
also-- W4BSG -- Grid EM64vr
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