combinations) A linear combination
of atomic orbitals (LCAO), which is a
‘building block’ of the LCAO orbitals
making up a *molecular orbital. The
SALC are constructed by group
theory appropriate for the symmetry
group of the molecule. SALC are used
in the construction of molecular orbitals.
salicylic acid (1-hydroxybenzoic
acid) A naturally occurring carboxylic acid, HOC 6 H 4 COOH, found in
certain plants; r.d. 1.44; m.p. 159°C;
sublimes at 211°C. It is used in the
foodstuffs and dyestuffs industries.
See also aspirin.
saline Describing a chemical compound that is a salt, or a solution
containing a salt.
salinometer An instrument for
measuring the salinity of a solution.
There are two main types: one is a
type of hydrometer to measure density; the other is an apparatus for
measuring the electrical conductivity
of the solution.
sal soda Anhydrous *sodium carbonate, Na 2 CO 3 .
salt A compound formed by reaction of an acid with a base, in which
the hydrogen of the acid has been replaced by metal or other positive
ions. Typically, salts are crystalline
ionic compounds such as Na
+
Cl
– and
NH 4
+ NO 3
–
. Covalent metal compounds, such as TiCl 4 , are also often
regarded as salts.
salt bridge An electrical connection made between two half cells. It
usually consists of a glass U-tube
Ülled with agar jelly containing a
salt, such as potassium chloride. A
strip of Ülter paper soaked in the salt
solution can also be used.
salt cake Industrial *sodium sulphate.
salting in See salting out.
salting out The effect in which the
solubility of a substance in a certain
solvent is reduced by the presence of
a second solute dissolved in the solvent. For example, certain substances
dissolved in water can be precipitated (or evolved as a gas) by addition
of an ionic salt. The substance is
more soluble in pure water than in
the salt solution. The opposite effect
involving an increase in solubility
may occur. This is known as salting
in.
saltpetre See nitre.
samarium Symbol Sm. A soft silvery metallic element belonging to
the *lanthanoids; a.n. 62; r.a.m.
150.35; r.d. 7.52 (20°C); m.p. 1077°C;
b.p. 1791°C. It occurs in monazite
and bastnatite. There are seven naturally occurring isotopes, all of which
are stable except samarium–147,
which is weakly radioactive (half-life
2.5 × 10
11 years). The metal is used
in special alloys for making nuclearreactor parts as it is a neutron absorber. Samarium oxide (Sm 2 O 3 ) is
used in small quantities in special optical glasses. The largest use of the element is in the ferromagnetic alloy
SmCo 5 , which produces permanent
magnets Üve times stronger than any
other material. The element was discovered by François Lecoq de Boisbaudran in 1879.
A
• Information from the WebElements site
sand Particles of rock with diameters in the range 0.06–2.00 mm. Most
sands are composed chieÛy of particles of quartz, which are derived
from the weathering of quartzbearing rocks.
Sandmeyer reaction A reaction of
diazonium salts used to prepare
chloro- or bromo-substituted aro471
Sandmeyer reaction
s
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of atomic orbitals (LCAO), which is a
‘building block’ of the LCAO orbitals
making up a *molecular orbital. The
SALC are constructed by group
theory appropriate for the symmetry
group of the molecule. SALC are used
in the construction of molecular orbitals.
salicylic acid (1-hydroxybenzoic
acid) A naturally occurring carboxylic acid, HOC 6 H 4 COOH, found in
certain plants; r.d. 1.44; m.p. 159°C;
sublimes at 211°C. It is used in the
foodstuffs and dyestuffs industries.
See also aspirin.
saline Describing a chemical compound that is a salt, or a solution
containing a salt.
salinometer An instrument for
measuring the salinity of a solution.
There are two main types: one is a
type of hydrometer to measure density; the other is an apparatus for
measuring the electrical conductivity
of the solution.
sal soda Anhydrous *sodium carbonate, Na 2 CO 3 .
salt A compound formed by reaction of an acid with a base, in which
the hydrogen of the acid has been replaced by metal or other positive
ions. Typically, salts are crystalline
ionic compounds such as Na
+
Cl
– and
NH 4
+ NO 3
–
. Covalent metal compounds, such as TiCl 4 , are also often
regarded as salts.
salt bridge An electrical connection made between two half cells. It
usually consists of a glass U-tube
Ülled with agar jelly containing a
salt, such as potassium chloride. A
strip of Ülter paper soaked in the salt
solution can also be used.
salt cake Industrial *sodium sulphate.
salting in See salting out.
salting out The effect in which the
solubility of a substance in a certain
solvent is reduced by the presence of
a second solute dissolved in the solvent. For example, certain substances
dissolved in water can be precipitated (or evolved as a gas) by addition
of an ionic salt. The substance is
more soluble in pure water than in
the salt solution. The opposite effect
involving an increase in solubility
may occur. This is known as salting
in.
saltpetre See nitre.
samarium Symbol Sm. A soft silvery metallic element belonging to
the *lanthanoids; a.n. 62; r.a.m.
150.35; r.d. 7.52 (20°C); m.p. 1077°C;
b.p. 1791°C. It occurs in monazite
and bastnatite. There are seven naturally occurring isotopes, all of which
are stable except samarium–147,
which is weakly radioactive (half-life
2.5 × 10
11 years). The metal is used
in special alloys for making nuclearreactor parts as it is a neutron absorber. Samarium oxide (Sm 2 O 3 ) is
used in small quantities in special optical glasses. The largest use of the element is in the ferromagnetic alloy
SmCo 5 , which produces permanent
magnets Üve times stronger than any
other material. The element was discovered by François Lecoq de Boisbaudran in 1879.
A
• Information from the WebElements site
sand Particles of rock with diameters in the range 0.06–2.00 mm. Most
sands are composed chieÛy of particles of quartz, which are derived
from the weathering of quartzbearing rocks.
Sandmeyer reaction A reaction of
diazonium salts used to prepare
chloro- or bromo-substituted aro471
Sandmeyer reaction
s
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