with sulphuric acid at 250°C and
leaching the product to give a solu-
tion of lithium sulphate. The carbon-
ate is then obtained by precipitation
with sodium carbonate solution.
Lithium carbonate is used in the pre-
vention and treatment of manic-
depressive disorders. It is also used
industrially in ceramic glazes.
lithium deuterideSee lithium hy-
dride.
lithium hydrideA white solid,
LiH; cubic; r.d. 0.82; m.p. 680°C; de-
composes at about 850°C. It is pro-
duced by direct combination of the
elements at temperatures above
500 °C. The bonding in lithium hy-
dride is believed to be largely ionic;
i.e. Li+H–as supported by the fact
that hydrogen is released from the
anode on electrolysis of the molten
salt. The compound reacts violently
and exothermically with water to
yield hydrogen and lithium hydrox-
ide. It is used as a reducing agent to
prepare other hydrides and the^2 H
isotopic compound, lithium
deuteride, is particularly valuable for
deuterating a range of organic com-
pounds. Lithium hydride has also
been used as a shielding material for
thermal neutrons.lithium hydrogencarbonate A
compound, LiHCO 3 , formed by the
reaction of carbon dioxide with aque-
ous lithium carbonate and known
only in solution. It has found medici-
nal uses similar to those of lithium
carbonate and is sometimes included
in proprietary mineral waters.
lithium hydroxide A white crys-
talline solid, LiOH, soluble in water,
slightly soluble in ethanol and insolu-
ble in ether. It is known as the mono-
hydrate (monoclinic; r.d. 1.51) and in
the anhydrous form (tetragonal, r.d.
1.46; m.p. 450°C; decomposes at
924 °C). The compound is made by re-acting lime with lithium salts or
lithium ores. Lithium hydroxide is
basic but has a closer resemblance to
group 2 hydroxides than to the other
group 1 hydroxides (an example of
theÜrst member of a periodic group
having atypical properties).
lithium oxide (lithia)A white crys-
talline compound, Li 2 O; cubic; r.d.
2.01; m.p. 1700°C. It can be obtained
from a number of lithium ores; the
main uses are in lubricating greases,
ceramics, glass and refractories, and
as aÛux in brazing and welding.
lithium sulphateA white or
colourless crystalline material,
Li 2 SO 4 , soluble in water and insoluble
in ethanol. It forms a monohydrate
(monoclinic; r.d. 1.88) and an anhy-
drous form, which exists in α- (mono-
clinic), β- (hexagonal) and γ- (cubic)
forms; r.d. 2.23. The compound is
prepared by the reaction of the hy-
droxide or carbonate with sulphuric
acid. It is not isomorphous with
other group 1 sulphates and does not
form alums.
lithium tetrahydroaluminate(III)
(lithium aluminium hydride; LAH)A
white or light grey powder, LiAlH 4 ;
r.d. 0.917; decomposes at 125°C. It is
prepared by the reaction of excess
lithium hydride with aluminium
chloride. The compound is soluble in
ethoxyethane, reacts violently with
water to release hydrogen, and is
widely used as a powerful reducing
agent in organic chemistry. It should
always be treated as a seriousÜre risk
in storage.
litmusA water-soluble dye ex-
tracted from certain lichens. It turns
red under acid conditions and blue
under alkaline conditions, the colour
change occurring over the pH range
4.5–8.3 (at 25°C). It is not suitable for
titrations because of the wide range
over which the colour changes, but islithium deuteride 330l