Alum Facts for Kids

This is Chrome alum, a type of alum made with chromium and potassium sulfate.

Alum is a cool word that can mean two things in chemistry. It can be a specific chemical compound, or it can refer to a whole group of similar compounds.

Think of it like this:

Sometimes, "alum" means a specific chemical called potassium aluminum sulfate. This is the most common type people talk about.
Other times, "alum" is a general name for a special kind of chemical called a double sulfate salt. These salts are made from two different metals and sulfate.

Here are some examples of different alums:

Potash alum is the common name for potassium aluminum sulfate.
Soda alum is another type, made with sodium aluminum sulfate.
Ammonium alum uses ammonium aluminum sulfate.

What is Alum?
- How Alum is Used
History of Alum
- Ancient Uses
Images for kids
See also

What is Alum?

Alum is a type of chemical compound. It is often found as clear or white crystals. These crystals can dissolve in water. Alum has a special taste that is often described as "astringent." This means it makes your mouth feel dry or puckered.

How Alum is Used

Alum has been used for a very long time in many different ways.

In medicine: People used alum to help stop bleeding from small cuts. It was also used to treat some skin problems.
In dyeing: Alum helps dyes stick better to fabrics like cloth. It acts as a "mordant," which means it helps the color become brighter and last longer.
In water treatment: Alum can be added to water to help clean it. It makes tiny particles in the water clump together, so they can be easily removed.
In food: Some types of alum are used in baking powder to help things rise.

History of Alum

People have known about and used alum for thousands of years. The word "alum" comes from an old Latin word, alumen.

Ancient Uses

The Roman writer Pliny the Elder wrote about alumen in his book Natural History. This was around 23 to 79 AD. He described different substances called alumen. All of them had that special astringent taste. They were all useful for dyeing clothes and for medicine. This shows that alum was an important material even in ancient times.