facture of certain paints, ceramics,
and paper. The naturally occurring
forms are used in the manufacture of
sulphuric acid.
Calgon Tradename for a watersoftening agent. See hardness of
water.
caliche A mixture of salts found in
deposits between gravel beds in the
Atacama and Tarapaca regions of
Chile. They vary from 4 m to 15 cm
thick and were formed by periodic
leaching of soluble salts during wet
geological epochs, followed by drying
out of inland seas in dry periods.
They are economically important as a
source of nitrates. A typical composition is NaNO 3 17.6%, NaCl 16.1%,
Na 2 SO 4 6.5%, CaSO 4 5.5%, MgSO 4
3.0%, KNO 3 1.3%, Na 2 B 4 O 7 0.94%,
KClO 3 0.23%, NaIO 3 0.11%, sand and
gravel to 100%.
californium Symbol Cf. A radioactive metallic transuranic element
belonging to the *actinoids; a.n. 98;
mass number of the most stable isotope 251 (half-life about 700 years).
Nine isotopes are known; californium–252 is an intense neutron
source, which makes it useful in neutron *activation analysis and potentially useful as a radiation source in
medicine. The element was Ürst produced by Glenn Seaborg (1912–99)
and associates in 1950.
A
• Information from the WebElements site
calixarenes Compounds that have
molecules with a cuplike structure
(the name comes from the Greek
calix, cup). The simplest, has four
phenol molecules joined by four
–CH 2 – groups into a ring (forming
the base of the ‘cup’). The four phenol hexagons point in the same direction to form a cavity that can bind
substrate molecules. Interest has
been shown in the potential ability
of calixarene molecules to mimic enzyme action.
calmodulin A protein, consisting
of 148 amino-acid residues, that acts
as a receptor for calcium ions in
many calcium-regulated processes in
both animal and plant cells. Calmodulin mediates reactions catalysed by
many enzymes.
calomel See mercury(i) chloride.
calomel half cell (calomel electrode) A type of half cell in which
the electrode is mercury coated with
calomel (HgCl) and the electrolyte is
a solution of potassium chloride and
saturated calomel. The standard electrode potential is –0.2415 volt (25°C).
In the calomel half cell the reactions
are
HgCl(s) ˆ Hg
+
(aq) + Cl
– (aq)
Hg
+ (aq) + e ˆ Hg(s)
The overall reaction is
HgCl(s) + e ˆ Hg(s) + Cl
– (aq)
This is equivalent to a Cl 2 (g)|Cl
– (aq)
half cell.
calorie The quantity of heat required to raise the temperature of 1
gram of water by 1°C (1 K). The calorie, a c.g.s. unit, is now largely replaced by the *joule, an *SI unit. 1
calorie = 4.186 8 joules.
Calorie (kilogram calorie; kilocalorie) 1000 calories. This unit is still in
limited use in estimating the energy
value of foods, but is obsolescent.
caloriÜc value The heat per unit
mass produced by complete combustion of a given substance. CaloriÜc
values are used to express the energy
values of fuels; usually these are expressed in megajoules per kilogram
(MJ kg
–1
). They are also used to measure the energy content of foodstuffs;
i.e. the energy produced when the
food is oxidized in the body. The
units here are kilojoules per gram
95
calorific value
c
www.AzShimi.ir www.AzShimi.com
and paper. The naturally occurring
forms are used in the manufacture of
sulphuric acid.
Calgon Tradename for a watersoftening agent. See hardness of
water.
caliche A mixture of salts found in
deposits between gravel beds in the
Atacama and Tarapaca regions of
Chile. They vary from 4 m to 15 cm
thick and were formed by periodic
leaching of soluble salts during wet
geological epochs, followed by drying
out of inland seas in dry periods.
They are economically important as a
source of nitrates. A typical composition is NaNO 3 17.6%, NaCl 16.1%,
Na 2 SO 4 6.5%, CaSO 4 5.5%, MgSO 4
3.0%, KNO 3 1.3%, Na 2 B 4 O 7 0.94%,
KClO 3 0.23%, NaIO 3 0.11%, sand and
gravel to 100%.
californium Symbol Cf. A radioactive metallic transuranic element
belonging to the *actinoids; a.n. 98;
mass number of the most stable isotope 251 (half-life about 700 years).
Nine isotopes are known; californium–252 is an intense neutron
source, which makes it useful in neutron *activation analysis and potentially useful as a radiation source in
medicine. The element was Ürst produced by Glenn Seaborg (1912–99)
and associates in 1950.
A
• Information from the WebElements site
calixarenes Compounds that have
molecules with a cuplike structure
(the name comes from the Greek
calix, cup). The simplest, has four
phenol molecules joined by four
–CH 2 – groups into a ring (forming
the base of the ‘cup’). The four phenol hexagons point in the same direction to form a cavity that can bind
substrate molecules. Interest has
been shown in the potential ability
of calixarene molecules to mimic enzyme action.
calmodulin A protein, consisting
of 148 amino-acid residues, that acts
as a receptor for calcium ions in
many calcium-regulated processes in
both animal and plant cells. Calmodulin mediates reactions catalysed by
many enzymes.
calomel See mercury(i) chloride.
calomel half cell (calomel electrode) A type of half cell in which
the electrode is mercury coated with
calomel (HgCl) and the electrolyte is
a solution of potassium chloride and
saturated calomel. The standard electrode potential is –0.2415 volt (25°C).
In the calomel half cell the reactions
are
HgCl(s) ˆ Hg
+
(aq) + Cl
– (aq)
Hg
+ (aq) + e ˆ Hg(s)
The overall reaction is
HgCl(s) + e ˆ Hg(s) + Cl
– (aq)
This is equivalent to a Cl 2 (g)|Cl
– (aq)
half cell.
calorie The quantity of heat required to raise the temperature of 1
gram of water by 1°C (1 K). The calorie, a c.g.s. unit, is now largely replaced by the *joule, an *SI unit. 1
calorie = 4.186 8 joules.
Calorie (kilogram calorie; kilocalorie) 1000 calories. This unit is still in
limited use in estimating the energy
value of foods, but is obsolescent.
caloriÜc value The heat per unit
mass produced by complete combustion of a given substance. CaloriÜc
values are used to express the energy
values of fuels; usually these are expressed in megajoules per kilogram
(MJ kg
–1
). They are also used to measure the energy content of foodstuffs;
i.e. the energy produced when the
food is oxidized in the body. The
units here are kilojoules per gram
95
calorific value
c
www.AzShimi.ir www.AzShimi.com