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Sodium hydroxide

physical science Maturity 9-11 Next article →

Sodium hydroxide is a white solid that people often call lye or caustic soda. It is an inorganic compound, which means it is not made from living things. This substance is a very strong base. A base is a type of chemical that can react with acids. Because it is so strong, it is also called highly corrosive. This means it can break down things like proteins and fats very quickly.

NaOH beads
NaOH beads

If it touches your skin, it can cause severe chemical burns. It is a very important tool in many different industries around the world.

There are many ways this chemical works in science and industry. When you mix solid sodium hydroxide with water, it creates an exothermic reaction. This means the process releases a large amount of heat. You must be careful because the heat could cause the liquid to splash.

NaOH - drain-cleaner
NaOH - drain-cleaner

The liquid feels slippery if it touches your skin. This happens because of a process called saponification. In this process, the chemical turns the natural oils on your skin into soap. It also works to clean out clogged drains and helps make paper and textiles.

In the past, people used a different way to make this substance. They used a method called causticizing. This involved treating sodium carbonate with calcium hydroxide. They used this because sodium hydroxide dissolves in water, but calcium carbonate does not. Later, a new way called the chloralkali process was found. This modern method is much faster because it produces the chemical in a single step. Today, most sodium hydroxide is made using this electrolytic process. It also creates chlorine gas as a byproduct.

There are many interesting numbers and facts about how much we use. In the year 2022, the world produced about 83 million dry tonnes of sodium hydroxide. This is a huge amount compared to 45 million tonnes produced in 1998. North America and Asia each produced about 14 million tonnes. Europe produced about 10 million tonnes. In the United States, a company named Olin is a major producer. They make about 5.7 million tonnes every year at many different sites.

Paint stripping with caustic soda
Paint stripping with caustic soda

You can see how this chemical works by looking at other things you know. For example, it can react with acids to make water and salt. If you mix it with hydrochloric acid, it creates sodium chloride. This is the same thing as common table salt.

Sodium hydroxide burn
Sodium hydroxide burn

It can also react with harmful gases like sulfur dioxide. This helps "scrub" or clean the air by removing bad gases from coal burning. It even helps treat drinking water by using aluminium hydroxide to filter out tiny bits of dirt. This makes the water much cleaner for people to use.

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🖼️ Images & Media (4)
File:NaOH - drain-cleaner.jpg
NaOH - drain-cleaner.jpg
File:Paint stripping with caustic soda.jpg
Paint stripping with caustic soda.jpg
File:Sodium hydroxide burn.png
Sodium hydroxide burn.png
File:NaOH beads.jpg
NaOH beads.jpg
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