Modern inorganic chemistry

Chlorine

GROUPS I AND II 123

Sodium

"Puddle-rod

Cathode

Gauze diaphragm

Figure 6,1. The Dowis cell

if necessary by the puddle-rod. The calcium, being almost immiscible
with sodium and much more dense, can readily be separated from
the molten sodium. The graphite anode wears away and must be
renewed from time to time.

USES

Lithium finds use in high -strength glass, and its use as a cathode in
high energy density batteries (which might be used in cars) has
been extensively investigated. Much sodium is used, as an alloy
with lead, in a reaction with ethyl chloride to produce tetraethyllead,
the "anti-knock' additive in petrol. Sodium is used to produce
sodium peroxide and sodium hydride. Liquid sodium, with its high
thermal conductivity, is used as a heat exchange liquid in fast-
breeder nuclear reactors, and in sodium-filled electrical transmission
lines. Potassium is used to make potassium superoxide KO 2 which
reacts with water and carbon dioxide to give oxygen,

4KO + 2HO + 4CO -» 4KHCO 3O

and which is therefore used as an emergency source of oxygen in,
for example, mines and submarines. Sodium-potassium alloys have
the same thermal properties as liquid sodium, with the additional
advantage that they are liquid at ordinary temperatures.