Sodium hydroxide is commonly called caustic soda because of its corrosive action on animal and vegetable tissues. Large quantity of sodium hydroxide is prepared by electrolytic process called the 'Chlor-alkali process'. Here, chlorine gas is given of at the anode and hydrogen gas at the cathode. Sodium hydroxide solution is formed near the cathode.
- Sodium hydroxide is a white deliquescent solid having melting point at 591 K (318°C)
- It is stable towards heat
- It is highly soluble in water and considerable amount of heat is evolved due to the formation of a number of hydrates e.g., NaOH.H2O, NaOH.2H2O. It is also soluble in alcohol
- Aqueous solution of sodium hydroxide is strongly alkaline due to its complete dissociation into Na+ and OH-
- Solution of sodium hydroxide is soapy to touch. It has a bitter taste. When a concentrated solution of sodium hydroxide comes in contact with skin, it breaks down the skin and flesh to a pasty mass.
- In the manufacture of soap, paper, viscose rayon (artificial silk), organic dyestuffs, and many other chemicals
- In the refining of petroleum and vegetable oils
- In the purification of bauxite for the extraction of aluminium
- As a cleansing agent and in washing powder for machines, metal sheets etc. It is too caustic to be used in washing clothes or hands
- For mercerizing cotton
- As a reagent in the laboratory
- In reclaiming rubber
- In the preparation of soda lime