Page 101 - Encyclopedia of Chemical Compounds 3 Vols

ALUMINUM OXIDE

Aluminum oxide. Turquoise
atoms are aluminum and
orange atoms are oxygen. Gray
sticks indicate double bonds.
PUBLISHERS RESOURCE GRO U P

The aluminum hydroxide (Al(OH 3 )) that is produced in this
reaction is then heated to drive off water, producing alumi-
num oxide. Wastes from coal mining operation are also treated
to extract the aluminum sulfate (Al 2 (SO 4 ) 3 ) they contain. The
aluminum sulfate is converted to aluminum hydroxide
which, again, is heated to produce aluminum oxide.

COMMON USES AND POTENTIAL HAZARDS
The primary use of aluminum oxide is the manufacture
of aluminum metal. When an electric current is passed
through molten (melted) aluminum oxide, the compound
breaks down to form aluminum metal and oxygen gas. The
method is called the Hall process after the American chemist
Charles Martin Hall who invented it.
Aluminum oxide is also widely used as an abrasive. An
abrasive is a very hard material used to grind, polish, sand,
scour, scrub, smooth or polish some other material. Among
the products that include aluminum oxide as an abrasive are
emery boards, sandpaper, grinding and polishing wheels and
belts, lens grinding devices, and gem polishing wheels.
The high melting point of aluminum oxide also makes it
a good refractory product. A refractory material is one that
does not melt easily, making it suitable for lining the inside

50 CHEMICAL COMPOUNDS