Caustic soda is the most typical of the strong alkalis.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 is highly hygroscopic, and absorbs the moisture, carbon dioxide, or sulfur dioxide in the air.
Caustic Soda Manufacturing Process
Metathesis Reaction
By reacting sodium carbonate with calcium hydroxide, the reaction yields sodium hydroxide and calcium carbonate. Since sodium hydroxide is soluble while calcium carbonate is not, by doing filtration, calcium carbonate can be easily removed to obtain a crude solution of sodium hydroxide. This solution is then 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 a main by-product. Electrolysis occurs through three main types of cells, mainly mercury cell, diaphragm cell and membrane cell.
Caustic Soda Properties
Parameter
|
Unit
|
Quantity
|
Molecular weight
|
g/mol
|
40
|
Melting point
crystallization begins |
°C
|
12-15
|
Specific gravity
|
°C, 20°C/20°C
|
1.53
|
Specific heat
|
(cal/gm/°C), 40°C-90°C
|
0.766
|
CAS number
|
1310-73-2
14014-06-3 (2H) 12179-02-1 (monohydrat) | |
IUPAC name
|
Sodium hydroxide
| |
Caustic Soda Application
It constitutes an essential reactant in the production of many useful organic chemicals (more than 30 % of caustic production goes into this application).
Inorganic chemicals like paints, glass and ceramics and uses in fuel cell production and cosmetics are also very important.
The paper, pulp and cellulose industries are major users of caustic soda.
Other areas where caustic is essential are: the food industry, water treatment(for the flocculation of heavy metals and acidity control), the soaps and detergents sectors, the textile sector (as a bleaching agent), mineral oils(preparation of greases and fuel additives) and the synthesis of the synthetic fibre rayon
About four per cent of caustic production is used in the process of refining aluminium from its ore bauxite.
The remainder of the caustic production (more than 17%) has miscellaneous applications, like the synthesis of pharmaceutical compounds, rubber recycling and the neutralisation of acids. It is also used to manufacture soap and detergents, applied during the saponification process in soap industry and neutralization process in detergent industry. Caustic soda saponifies fats into water soluble sodium-based soaps.