Page 100 - Encyclopedia of Chemical Compounds 3 Vols

O O O
Al Al

OTHER NAMES:
Alumina
FORMULA: Aluminum Oxide
Al 2 O 3
ELEMENTS:
Aluminum, oxygen
OVERVIEW
COMPOUND TYPE: KE
Metallic oxide Aluminum oxide (uh-LOO-min-um OK-side) is white crystal-
line powder that occurs in nature in a variety of minerals,
STATE:
Y
including boehmite, bayerite, corundum, diaspore, and gibb-
Solid
site. Corundum is second hardest naturally occurring mineral.
F
MOLECULAR WEIGHT: A Only diamond is harder. Aluminum oxide occurs in a variety of
101.96 g/mol C chemical forms in a variety of gemstones, including chryso-
beryl, ruby, sapphire, and spinel. The color of these gemstones
MELTING POINT: T

2072 C (3762 F) is a result of impurities, such as chromium (in the case of ruby)
and iron and titanium (in the case of sapphire). The colors may
S
BOILING POINT: also vary depending on the kind and amount of each impurity.

2980 C (5396 F)
Aluminum oxide’s commercial uses depend not only on its
SOLUBILITY: hardness, but also on its high melting point and its low elec-
Insoluble in water and trical conductivity. The compound is also non-combustible and
most organic sol- resistant to attack by most solvents and other chemical agents.
vents; slowly soluble
in basic solutions.
HOW IT IS MADE
Aluminum oxide is produced by washing the rocky mate-
rial bauxite with a hot solution of sodium hydroxide (NaOH).

CHEMICAL COMPOUNDS 49