ally because the single step is too
inefÜcient to produce the desired result. For example, in various uranium-enrichment processes the
separation of the desired isotope is
only poorly achieved in a single
stage; to achieve better separation
the process has to be repeated a
number of times, in a series, with
the enriched fraction of one stage
being fed to the succeeding stage for
further enrichment. Another example of cascade process is that operating in a *cascade liqueÜer.
case hardening The hardening of
the surface layer of steel, used for
tools and certain mechanical components. The commonest method is to
carburize the surface layer by heating the metal in a hydrocarbon or by
dipping the red hot metal into
molten sodium cyanide. Diffusion of
nitrogen into the surface layer to
form nitrides is also used.
casein One of a group of phosphate-containing proteins (phosphoproteins) found in milk. Caseins are
easily digested by the enzymes of
young mammals and represent a
major source of phosphorus.
CAS registry A database of chemical compounds, certain mixtures,
and biological sequences maintained
by the Chemical Abstracts Service of
the American Chemical Society. In
the registry every entry has a unique
CAS registry number (CASRN). This
has three parts: up to six digits, followed by two digits, followed by one
digit. For example, the CAS number
of water is 7732-18-5. The Ünal digit
is a check number. CAS registry
numbers are used for searching
chemical databases. The size of the
registry is immense, with over 32
million substances and 59 million sequences. It identiÜes every chemical
that has been described in the literature since 1957 and around 50 000
new numbers are added each week.
A
• Further information from the CAS site
• A free service for Ünding CAS numbers
from CambridgeSoft
cassiterite A yellow, brown, or
black form of tin(IV) oxide, SnO 2 ,
that forms tetragonal, often twinned,
crystals; the principal ore of tin. It occurs in hydrothermal veins and metasomatic deposits associated with acid
igneous rocks and in alluvial (placer)
deposits. The chief producers are
Malaysia, Indonesia, Democratic Republic of Congo, and Nigeria.
cast iron A group of iron alloys
containing 1.8 to 4.5% of carbon. It is
usually cast into speciÜc shapes ready
for machining, heat treatment, or assembly. It is sometimes produced direct from the *blast furnace or it
may be made from remelted *pig
iron.
Castner–Kellner cell An electrolytic cell used industrially for the
production of *sodium hydroxide.
The usually iron cell is Ülled with
brine (sodium chloride solution) and
employs liquid mercury as the cathode. The sodium liberated there
forms an amalgam with the mercury,
which is run off and reacted with
water to give sodium hydroxide (and
hydrogen); the mercury is then reused. Chlorine gas produced at the
anode is another valuable by-product.
castor oil A pale-coloured oil extracted from the castor-oil plant. It
contains a mixture of glycerides
of fatty acids, the predominant
acid being ricinoleic acid,
C 17 H 32 (OH)COOH. It is used as a
*drying oil in paints and varnishes
and medically as a laxative.
catabolism The metabolic breakdown of large molecules in living orcase hardening
106
c
www.AzShimi.ir www.AzShimi.com
inefÜcient to produce the desired result. For example, in various uranium-enrichment processes the
separation of the desired isotope is
only poorly achieved in a single
stage; to achieve better separation
the process has to be repeated a
number of times, in a series, with
the enriched fraction of one stage
being fed to the succeeding stage for
further enrichment. Another example of cascade process is that operating in a *cascade liqueÜer.
case hardening The hardening of
the surface layer of steel, used for
tools and certain mechanical components. The commonest method is to
carburize the surface layer by heating the metal in a hydrocarbon or by
dipping the red hot metal into
molten sodium cyanide. Diffusion of
nitrogen into the surface layer to
form nitrides is also used.
casein One of a group of phosphate-containing proteins (phosphoproteins) found in milk. Caseins are
easily digested by the enzymes of
young mammals and represent a
major source of phosphorus.
CAS registry A database of chemical compounds, certain mixtures,
and biological sequences maintained
by the Chemical Abstracts Service of
the American Chemical Society. In
the registry every entry has a unique
CAS registry number (CASRN). This
has three parts: up to six digits, followed by two digits, followed by one
digit. For example, the CAS number
of water is 7732-18-5. The Ünal digit
is a check number. CAS registry
numbers are used for searching
chemical databases. The size of the
registry is immense, with over 32
million substances and 59 million sequences. It identiÜes every chemical
that has been described in the literature since 1957 and around 50 000
new numbers are added each week.
A
• Further information from the CAS site
• A free service for Ünding CAS numbers
from CambridgeSoft
cassiterite A yellow, brown, or
black form of tin(IV) oxide, SnO 2 ,
that forms tetragonal, often twinned,
crystals; the principal ore of tin. It occurs in hydrothermal veins and metasomatic deposits associated with acid
igneous rocks and in alluvial (placer)
deposits. The chief producers are
Malaysia, Indonesia, Democratic Republic of Congo, and Nigeria.
cast iron A group of iron alloys
containing 1.8 to 4.5% of carbon. It is
usually cast into speciÜc shapes ready
for machining, heat treatment, or assembly. It is sometimes produced direct from the *blast furnace or it
may be made from remelted *pig
iron.
Castner–Kellner cell An electrolytic cell used industrially for the
production of *sodium hydroxide.
The usually iron cell is Ülled with
brine (sodium chloride solution) and
employs liquid mercury as the cathode. The sodium liberated there
forms an amalgam with the mercury,
which is run off and reacted with
water to give sodium hydroxide (and
hydrogen); the mercury is then reused. Chlorine gas produced at the
anode is another valuable by-product.
castor oil A pale-coloured oil extracted from the castor-oil plant. It
contains a mixture of glycerides
of fatty acids, the predominant
acid being ricinoleic acid,
C 17 H 32 (OH)COOH. It is used as a
*drying oil in paints and varnishes
and medically as a laxative.
catabolism The metabolic breakdown of large molecules in living orcase hardening
106
c
www.AzShimi.ir www.AzShimi.com