Alum – Potassium aluminum sulfate – Potassium alum

What is Alum?

Alum is a naturally occurring chemical compound known as a double salt, consisting of aluminium, sulfate, and an alkali ion such as potassium or ammonium. The most common form is potassium alum with the chemical formula KAl(SO₄)₂ 12H₂O. It is a colourless, white crystalline powder that is readily soluble in water. Without further specification, alum is also called potassium aluminium sulfate.

Properties and Uses of Potassium Alum

Alum plays an important role in various traditional and modern processes due to its unique chemical properties. In papermaking, it was traditionally used to improve the properties of the paper. It was added to the pulp to strengthen the structure and make the paper more resistant to ink. This reduces the absorption of ink by the fibres, allowing for sharper printing. This application is less common today, but it remains a historically important ingredient in the development of the paper industry. In tanning, potassium alum is an essential tool. It is used in the tanning of leather to preserve and soften the hides. Due to its astringent effect, it stabilises the fibres in the hide, making the leather more supple and resistant to wear. It is mainly used in the production of white leather, giving the leather a smooth, light finish without dark discolouration. In textile dyeing, alum is often used as a mordant. It improves the adhesion of dyes to the fabric and thus ensures better colour fastness. Pre-treating fabrics with this substance optimizes the chemical reaction between the fibers and the dye, resulting in more intense and durable colors. Alum is widely used in water purification. It acts as a coagulant and helps remove dirt particles and other impurities from water. It causes small particles to clump together into larger flakes, which then sink to the bottom or can be easily filtered. This process makes it an indispensable substance in water purification plants and in the purification of drinking water. In horticulture, alum is valued for its ability to lower the pH of the soil. Acid-loving plants, such as hydrangeas, benefit from the addition of this substance to the soil. By making the soil more acidic, it creates an optimal environment for these plants, which is especially visible in the vibrant colors of hydrangeas.

FREQUENTLY ASKED QUESTIONS – FAQ

Is potassium alum the same as alum?

Yes, potassium alum is a common form of alum. It is a general term for a group of double salts of aluminum and sulfate, combined with another ion such as potassium or ammonium. Potassium alum (KAl(SO₄)₂ 12H₂O) is the most commonly used variety and is often simply called “alum”.

Is Alum Dangerous?

Generally it is not dangerous when used properly. When in contact with skin or mucous membranes it can be slightly irritating, especially for sensitive individuals. Avoid inhaling the powder and avoid contact with eyes.

What forms of alum are there?

The two most common forms are:

1. Potassium alum (KAl(SO₄)₂·12H₂O) – widely used in personal care, water purification, and tanning.
2. Ammonium alum (NH₄Al(SO₄)₂·12H₂O) – often used in similar processes, depending on specific needs.
   Both variants have similar properties, but the choice depends on the application.

Is Alum Poisonous?

It is non-toxic in normal use and is considered safe for humans and the environment. However, in large quantities or prolonged exposure it can cause irritation to the skin, eyes or respiratory tract. Caution is advised when handling this powder form.

Buy alum

Are you looking for alum? You have come to the right place. Simply order online with just one click. Once your order is received, we will ensure fast and reliable delivery, so that you will have your potassium alum at home as soon as possible!