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2. s-Block Elements eLearn.Punjab

2.4 COMMERCIAL PREPARATION OF SODIUM HYDROXIDE
BY THE DIAPHRAGM CELL

Sodium hydroxide is manufactured Fig.2.2(a) Nelson Cell for the
on a large scale by the electrolysis Production of NaOH
of aqueous solution of common
salt in a diaphragm cell Fig. 2.2 (a)

The cell is made of steel tank.
An oblong perforated steel vessel
lined inside with asbestos diaph-
ragm serves as a cathode. It is
provided with a constant level
device to keep the vessel filled to
the specified level with brine. A
graphite anode is held within the
U shaped diaphragm and it projects
into the salt solution. The steam is
blown during the process which
keeps the electrolyte warm and
helps to keep the perforations clear.

The chlorine released at the anode,
rises into the dome at the top while
hydrogen released at the cathode,
escapes through a pipe. The
sodium hydroxide solution slowly
percholates into a catch basin.

Fig.2.2(b)

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