Page 202 - Encyclopedia of Chemical Compounds 3 Vols

Ca O

OTHER NAMES:
Lime; quicklime;
burnt lime; calx;
unslaked lime;
fluxing lime

FORMULA:
CaO
Calcium Oxide
ELEMENTS:
Calcium, oxygen
COMPOUND TYPE:
Metallic oxide
OVERVIEW
STATE: KE
Calcium oxide (KAL-see-um OK-side) is an odorless crystal-
Solid
line or powdery solid that, in a pure form, is white to off-gray. It
Y
often appears with a yellowish or brownish tint to the presence
56.08 g/mol of impurities, especially iron. Calcium oxide reacts with water
MOLECULAR WEIGHT: F
to form calcium hydroxide (Ca(OH) 2 ) with the evolution of
A

2,898 C(5,248 F) significant amounts of heat. The compound is strongly caustic.
MELTING POINT: C
Calcium oxide has been known since ancient times. The
T
Not available Roman writer Cato the Elder (234–149 BCE) described one
BOILING POINT: S
method of producing the compound in 184 BCE. Another early
SOLUBILITY:
Roman scholar, Pliny the Elder (23–79 CE) discussed the com-
Reacts with water
pound at length in his book Historia Naturalis (Natural
to form calcium
History), published in 70 CE. By the early fifteenth century,
hydroxide; soluble in
most of Europe was using calcium oxide (widely referred to
acids; insoluble in
alcohol and most as lime) in the construction of buildings. The Scottish che-
organic solvents mist Joseph Black (1728–1799) carried out some of the ear-
liest scientific studies of calcium oxide. He found that when
the compound is exposed to air, it combines with carbon
dioxide to form calcium carbonate.
CHEMICAL COMPOUNDS 151