Caustic soda is used to make soaps, rayom, paper, explosives, dyestuffs, and petroleum products. It is also used in processing cotton fabric, laundering and bleaching, metal cleaning and processing, oxide coating, electroplating, and electrolytic extracting. It is commonly present in commercial drain and oven cleaners.Caustic soda is mainly used in textile in the form of caustic soda flakes or pearls. It is also known as sodium hydroxide, has a white solid appearance and a formula of NaOH. It is an inorganic alkali salt, hygroscopic in nature and is soluble in water and polar solvents. It has a slippery feel and also absorbs carbon dioxide in the atmosphere to from sodium carbonate.
Properties of caustic soda:
- Highly soluble in water & dissolution is highyly exothermic.
- Low solubility in ethanol & methanol.
- Insoluble in ether & other non-polar solvents.
- Strong base.
- Readily absorbs water (hygroscopic) and carbon dioxide from the air.
- Strong electrolyte.
- Not volatile, but can rise easily in air as an aerosol.
Manufacturing process of caustic soda:
- Metathesis reaction – By reacting sodium carbonate with calcium hydroxide, sodium hydroxide and calcium carbonate is produced. These products can be easily separated by filtration as calcium carbonate is not soluble whereas sodium hydroxide is highly soluble. The solution will then be purified, processed and standardized for industrial consumption.
- Chloralkali process – With the electrolysis of sodium chloride solution, solid sodium hydroxide is manufactured and obtained with the evaporation of water. Chlorine gas is also produced as the main by-product. This is done through three main types of cell, mainly mercury cell, diaphragm cell and the membrane cell.