Chlorine (Cl2)

Direct current electrolysis of aqueous sodium chloride solutions produces chlorine, sodium hydroxide and hydrogen. The overall chemical reaction is as follows:

involving two electrons.

The general principle of the process requires five main sections:

• brine purification treatment ;

• electrolysis room ;

• chlorine treatment ;

• to obtain 50% soda ash by mass;

• hydrogen treatment ;

and can be represented by the schematic diagram in figure 1 .

The basic principle of electrolysis cells is to keep the two gases (chlorine and hydrogen) separate for safety reasons (violent reaction between the two gases) and the two products (chlorine and soda) liable to recombine.

There are three different electrolysis processes currently in use:

• the first with a mercury cathode, known as the "mercury" process;

• the second with a percolating diaphragm as a separator between the anode and cathode chambers, known as the "diaphragm" process;

• the third with an ion exchange membrane as a separator between the anode and cathode chambers, known as the "membrane" process.