Sodium Hydroxide (NaOH) also called caustic soda or lye is an odourless corrosive white crystalline solid and an extremely caustic metallic base that is made up of sodium (Na) cations and hydroxide (OH) anions.
It is highly soluble in water and absorbs carbon dioxide and moisture from the air and so should be stored in an airtight material. However, despite its white flake and hard appearance when pure, its solution is a colourless liquid that has denser than water.
This orthogonal crystal which is regarded as the most widely used industrial alkali is extremely corrosive to animal and plant tissue and metals. Its ability to test a large number of cations and provide the required alkaline mediums also makes it the most commonly used base in chemical laboratories.
When dissolved in water, it forms alkaline solutions which can be used in the treatment of cellulose, removing organic and sulfuric acid and the manufacturing of some chemicals.
It is very versatile and can be used in many industries which range from the petroleum industry to the pharmaceutical industry, and can also be used in the production of household equipment like paper, soaps, detergents and many others.
Total world production of this chemical was around 45 million tonnes in the last analysis done in 1998, with 10 million tonnes being produced by Europe and a further 14 million tonnes being produced by Asia and North America.
Preparation of Sodium Hydroxide
Industrially, sodium hydroxide along with chlorine and hydrogen gas is produced using the Chlor-alkali process.
The Chlor-alkali process is classified into three processes: the diaphragm cell process, the mercury cell process and the membrane cell process which is regarded as most economically viable due to its minimal use of electricity and the most environmental friendly compared to the former two processes.
In this process, a membrane cell with positive and negative charged electrodes are impressed into concentrated sodium chloride solution (brine) and forms chlorine gas when a negative charge (anode) oxidizes a chloride ion and forms hydrogen gas when a positive charge (cathode) oxidizes hydrogen ions.
Sodium hydroxide is then formed when sodium ions are allowed to pass through the semi-permeable membrane cell and react with water.
2NaCl(aq) + 2H2O(l) = 2NaOH(aq) + Cl2(l) + H2 (l)
Chemical Properties of Sodium Hydroxide
Sodium Hydroxide reacts with acids like hydrochloric acid to form water and corresponding salts like sodium chloride.
Furthermore, heat is released when a strong acid is used in this reaction.
This reaction is made possible by the hydroxide ion in sodium hydroxide which makes it a strong base.
The addition of water to concentrated or solid sodium hydroxide forms an exothermic dilution, hence heat is released, while the addition of heat to a dilute sodium hydroxide enhances its concentration by evaporating the water.
Sodium Hydroxide isn’t corrosive to copper or iron but is corrosive to metals like zinc and aluminium.
This makes lye a very bad choice for cleaning materials made with aluminium.
Sodium Hydroxide also forms salts when it reacts with phenols and non-metals like silicon and phosphorus.
Physical Properties of Sodium Hydroxide
Sodium Hydroxide is an odourless and opaque crystal that is white and solid when pure.
It is soluble in water and glycerol, slightly soluble in methanol and ethanol and insoluble in ether and other non-polar solvents.
It has a density of 2.13 g/cm3 and a Molar Mass of 39.9971 g/mol-1. Its melting point is 318 in °C and 604 in °F, while its boiling point is 1,388 °C and 2,530 °F.
Uses of Sodium Hydroxide
• It is used to neutralize acids.
• It is used in making artificial textile fibers like Rayon.
• It is used in regulating pH.
• It is used to increase a mixture’s alkalinity.
• It is used in organic synthesis.
• It is used to treat pretzel dough and bagels.
• It is used to produce soaps and detergent.
However, they are used mostly to produce bar soaps and other solid detergents rather than liquid soaps because that makes them easier to transport and store.
• It is used in the Bayer process which involves the purification of bauxite ore and extraction of aluminium metal.
• It is used in the drilling process in the petroleum industry.
• It is used in degreasing metals.
• It is used to carry out caustic washing – which is the process of treating poor quality crude oil and removing sulfurous impurities.
• When added to water and heated, it can be used industrially as a cleaning agent for various equipment like storage tanks etc.
• It is used in making dyes and bleaches.
• In the food industry, it is used as a component in the crust of baked cakes, processing soft drinks, softening of olives, thickening of ice cream, processing of cocoa among others.
• It is used as an ingredient in hair relaxers. However, these kinds of relaxers are used by professionals cause misuse could cause chemical burns.
• It is used as a paint remover on wooden surfaces.
• It is used in the water purification process to increase the pH of water supplies.
This process reduces the number of toxic metals that can dissolve into the water.
• It is used in the mixing process of cement to ensure its workability.
• It is used to produce pharmaceutical products like aspirin and many others.
• It is used in the production of fuel cells.
Due to its corrosive nature, it can disintegrate protein and lipids in living tissues and cause severe chemical burns if it comes in contact with your skin. And If it comes in contact with your eye, it can lead to permanent blindness.
If ingested, it could also cause severe harm to your body system.
Drinking it will lead to immediate vomiting, diarrhoea, swallowing difficulties, stomach pain, nausea, damage to your mouth, throat and stomach.
Furthermore, during the dissolution of sodium hydroxide and its reaction with acids, it produces energy in form of heat which might cause heat burns and could also lead to coughing and difficulty in breathing and even permanent damage to the lung. It can also make combustible materials burn.
So, it is advisable to use protective equipment for your hands, eyes and other safety clothing when handling this chemical.
Adequate storage of this chemical is highly recommended because if stored wrongly, it could cause a lot of harm.