soda or caustic lye is sodium hydroxide. It is an inorganic and highly alkaline
compound available in the several forms. It is a strong base and is extensively
used chemical and has varied applications. The major user of caustic soda are
aluminum industry, pulp and paper industry and chemical industry.
forms of Caustic Soda
Caustic Soda : Liquid caustic soda is dangerous compared to its solid form
are two methods for the production of sodium hydroxide: Solvay process and
soda ash obtained from the Solvay process is treated with calcium hydroxide in
a double displacement reaction, where the carbonate is replaced by the
hydroxide ion to produce sodium hydroxide.
+ Ca(OH)2 Ã? 2NaOH
chloroalkali process replaced the Solvay process and is preferred over it. It
is used in the production of chlorine gas and caustic soda is a by-product. In
this process, saturated brine is passed over the electrolytic cell, which
ionizes the sodium and chlorine ions. At the anode, it oxidizes to chlorine
gas. Water at the cathode is reduced to hydrogen and hydroxide ions.
2Cl- Ã? Cl2
2H2O + 2e- Ã? H2
ion-permeable membrane allows the passage of sodium ions which reacts with
hydroxide ions to from sodium hydroxide in solution. Three types of cells are
used in this process namely, Mercury cell, diaphragm cell, membrane cell.