otherwise randomly arranged. Cholesteric and smectic liquid crystals
also have aligned molecules, which
are arranged in distinct layers. In
cholesteric crystals, the axes of the
molecules are parallel to the plane of
the layers; in smectic crystals they
are perpendicular.
liquid-crystal polymer A polymer
with a liquid-crystal structure, this
being the most thermodynamically
stable. Liquid-crystal polymers contain long rigid chains and combine
strength with lightness. They are,
however, difÜcult to produce commercially.
liquidus A line on a phase diagram
above which a substance is liquid.
l-isomer See optical activity.
L-isomer See absolute configuration.
litharge See lead(ii) oxide.
lithia See lithium oxide.
lithium Symbol Li. A soft silvery
metal, the Ürst member of group 1
(formerly IA) of the periodic table
(see alkali metals); a.n. 3; r.a.m.
6.939; r.d. 0.534; m.p. 180.54°C; b.p.
1347°C. It is a rare element found in
spodumene (LiAlSi 2 O 6 ), petalite
(LiAlSi 4 O 10 ), the mica lepidolite, and
certain brines. It is usually extracted
by treatment with sulphuric acid to
give the sulphate, which is converted
to the chloride. This is mixed with a
small amount of potassium chloride,
melted, and electrolysed. The stable
isotopes are lithium–6 and lithium–7.
Lithium–5 and lithium–8 are shortlived radioisotopes. The metal is used
to remove oxygen in metallurgy and
as a constituent of some Al and Mg
alloys. It is also used in batteries and
is a potential tritium source for fusion research. Lithium salts are used
in psychomedicine. The element reacts with oxygen and water; on heating it also reacts with nitrogen and
hydrogen. Its chemistry differs somewhat from that of the other group 1
elements because of the small size of
the Li
+ ion.
A
• Information from the WebElements site
lithium aluminium hydride See
lithium tetrahydroaluminate(iii).
lithium battery A type of voltaic
cell containing lithium or lithium
compounds. The most commonly
used has a metallic lithium anode
and a manganese dioxide (MnO 2 )
cathode, the electrolyte being a solution of lithium salts in an organic solvent. Batteries of this type have an
output of about 3 volts. They are
more expensive than alkaline batteries, but last longer. Li–MnO 2 batteries
are also produced in a Ûat disk form
for use in digital watches and other
small portable devices. A number of
other more specialized lithium primary batteries are available but are
not in general use.
The lithium-ion battery is a
rechargeable cell. The anode is carbon and the cathode is a metal oxide
(e.g. cobalt(IV) oxide, CoO 2 ). The electrolyte is a lithium salt such as the
borate (LiBO 4 ) or chlorate (LiClO 4 ) in
an organic solvent. The action of the
cell depends on movement of Li ions
between anode and cathode with oxidation of the cobalt ions during
charging and reduction during discharge. Lithium-ion batteries are
light and have a low self-discharge
rate, although the capacity does deteriorate with age. They are extensively
used in mobile phones, laptops, camcorders, and similar devices, as well
as electric cars.
lithium carbonate A white solid,
Li 2 CO 3 ; r.d. 2.11; m.p. 723°C; decomposes above 1310°C. It is produced
commercially by treating the ore
329
lithium carbonate
l
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also have aligned molecules, which
are arranged in distinct layers. In
cholesteric crystals, the axes of the
molecules are parallel to the plane of
the layers; in smectic crystals they
are perpendicular.
liquid-crystal polymer A polymer
with a liquid-crystal structure, this
being the most thermodynamically
stable. Liquid-crystal polymers contain long rigid chains and combine
strength with lightness. They are,
however, difÜcult to produce commercially.
liquidus A line on a phase diagram
above which a substance is liquid.
l-isomer See optical activity.
L-isomer See absolute configuration.
litharge See lead(ii) oxide.
lithia See lithium oxide.
lithium Symbol Li. A soft silvery
metal, the Ürst member of group 1
(formerly IA) of the periodic table
(see alkali metals); a.n. 3; r.a.m.
6.939; r.d. 0.534; m.p. 180.54°C; b.p.
1347°C. It is a rare element found in
spodumene (LiAlSi 2 O 6 ), petalite
(LiAlSi 4 O 10 ), the mica lepidolite, and
certain brines. It is usually extracted
by treatment with sulphuric acid to
give the sulphate, which is converted
to the chloride. This is mixed with a
small amount of potassium chloride,
melted, and electrolysed. The stable
isotopes are lithium–6 and lithium–7.
Lithium–5 and lithium–8 are shortlived radioisotopes. The metal is used
to remove oxygen in metallurgy and
as a constituent of some Al and Mg
alloys. It is also used in batteries and
is a potential tritium source for fusion research. Lithium salts are used
in psychomedicine. The element reacts with oxygen and water; on heating it also reacts with nitrogen and
hydrogen. Its chemistry differs somewhat from that of the other group 1
elements because of the small size of
the Li
+ ion.
A
• Information from the WebElements site
lithium aluminium hydride See
lithium tetrahydroaluminate(iii).
lithium battery A type of voltaic
cell containing lithium or lithium
compounds. The most commonly
used has a metallic lithium anode
and a manganese dioxide (MnO 2 )
cathode, the electrolyte being a solution of lithium salts in an organic solvent. Batteries of this type have an
output of about 3 volts. They are
more expensive than alkaline batteries, but last longer. Li–MnO 2 batteries
are also produced in a Ûat disk form
for use in digital watches and other
small portable devices. A number of
other more specialized lithium primary batteries are available but are
not in general use.
The lithium-ion battery is a
rechargeable cell. The anode is carbon and the cathode is a metal oxide
(e.g. cobalt(IV) oxide, CoO 2 ). The electrolyte is a lithium salt such as the
borate (LiBO 4 ) or chlorate (LiClO 4 ) in
an organic solvent. The action of the
cell depends on movement of Li ions
between anode and cathode with oxidation of the cobalt ions during
charging and reduction during discharge. Lithium-ion batteries are
light and have a low self-discharge
rate, although the capacity does deteriorate with age. They are extensively
used in mobile phones, laptops, camcorders, and similar devices, as well
as electric cars.
lithium carbonate A white solid,
Li 2 CO 3 ; r.d. 2.11; m.p. 723°C; decomposes above 1310°C. It is produced
commercially by treating the ore
329
lithium carbonate
l
www.AzShimi.ir www.AzShimi.com