temperatures at standard pressure of
ice in equilibrium with water (0°C)
and water in equilibrium with steam
(100°C). The scale, between these two
temperatures, is divided in 100 de-
grees. The degree Celsius (°C) is equal
in magnitude to the *kelvin. This
scale was formerly known as the
centigrade scale; the name was ofÜ-
cially changed in 1948 to avoid con-
fusion with a hundredth part of a
grade. It is named after the Swedish
astronomer Anders Celsius (1701–44),
who devised the inverted form of
this scale (ice point 100°, steam point
0 °) in 1742.
cementAny of various substances
used for bonding or setting to a hard
material. Portland cement is a mix-
ture of calcium silicates and alumi-
nates made by heating limestone
(CaCO 3 ) with clay (containing alumi-
nosilicates) in a kiln. The product is
ground to aÜne powder. When
mixed with water it sets in a few
hours and then hardens over a
longer period of time due to the for-
mation of hydrated aluminates and
silicates.
cementationAny metallurgical
process in which the surface of a
metal is impregnated by some other
substance, especially an obsolete
process for making steel by heating
bars of wrought iron to red heat for
several days in a bed of charcoal. See
also case hardening.
cementite See steel.
centi-Symbol c. A preÜx used in
the metric system to denote one hun-
dredth. For example, 0.01 metre = 1
centimetre (cm).
centigrade scaleSee celsius
scale.
centrifugal pumpSee pump.
centrifugeA device in which solid
or liquid particles of different densi-
ties are separated by rotating them in
a tube in a horizontal circle. The
denser particles tend to move along
the length of the tube to a greater ra-
dius of rotation, displacing the
lighter particles to the other end.
ceramicsInorganic materials, such
as pottery, enamels, and refractories.
Ceramics are metal silicates, oxides,
nitrides, etc.
cerebroside Any one of a class of
*glycolipids in which a single sugar
unit is bound to a sphingolipid (see
phospholipid). The most common
cerebrosides are galactocerebrosides,
containing the sugar group galactose;
they are found in the plasma mem-
branes of neural tissue and are abun-
dant in the myelin sheaths of
neurones.ceriumSymbol Ce. A silvery metal-
lic element belonging to the *lan-
thanoids; a.n. 58; r.a.m. 140.12; r.d.
6.77 (20°C); m.p. 799°C; b.p. 3426°C.
It occurs in allanite, bastnasite,
cerite, and monazite. Four isotopes
occur naturally: cerium–136, –138,
–140, and –142;Üfteen radioisotopes
have been identiÜed. Cerium is used
in mischmetal, a rare-earth metal
containing 25% cerium, for use in
lighterÛints. The oxide is used in
the glass industry. It was discovered
by Martin Klaproth (1743–1817) in
1803.
A- Information from the WebElements site
cermetA composite material con-
sisting of a ceramic in combination
with a sintered metal, used when a
high resistance to temperature, cor-
rosion, and abrasion is needed.cerussiteAn ore of lead consisting
of lead carbonate, PbCO 3. It is usually
of secondary origin, formed by the
weathering of *galena. Pure cerussite
is white but the mineral may be grey111 cerussite
c