What Is Hydrogen Peroxide?

by Lucy Bell-Young

Hydrogen peroxide (H2O2) is a chemical compound that is widely used as a weak oxidising acid and as a component in cleaning products. Today, we’re looking at the chemistry behind this popular substance.

A Short History of Hydrogen Peroxide

The history of hydrogen peroxide begins in 1799 when Prussian scientist Alexander von Humboldt (who, as an aside, was also a geographer, naturalist, explorer, philosopher, and polymath – and all-round busy genius) made the first synthetic peroxide. This was barium peroxide and was produced as a byproduct of von Humboldt’s experiments to decompose air.

Almost twenty years later, French chemist Louis Jacques Thénard used barium peroxide to make ‘eau oxygénée’, or oxygenated water. This later became known as hydrogen peroxide. Through the nineteenth century, chemists improved the methods and processes used to produce hydrogen peroxide. However, the first person to produce pure hydrogen peroxide was German chemist Richard Wolffenstein, who in 1894 used vacuum distillation to make H2O2.

It wasn’t until the mid-twentieth century that a way was found to produce hydrogen peroxide on an industrial scale.

Hydrogen Peroxide Formula

Hydrogen peroxide is an inorganic peroxide made up of two hydroxy groups that are joined by a covalent oxygen-oxygen single bond. Its chemical formula is H2O2.

Properties of Hydrogen Peroxide

Hydrogen peroxide is the simplest of all the peroxides (compounds containing an oxygen-oxygen single bond). It is mostly a clear and colourless liquid. However, it can appear pale blue in its pure form. It is also:

  • Slightly more viscous than water
  • Nonpolar with twisted C2 symmetry
  • Corrosive to the skin in solutions above 8%
  • Thermodynamically unstable

As an unstable compound, hydrogen peroxide decomposes when exposed to heat, bases or catalysts. Therefore, it is usually kept in a slightly acidic solution in the presence of a stabiliser.

Grades of Hydrogen Peroxide

Hydrogen peroxide comes in various grades, or levels of concentration, depending on its end-use.

  • 3% hydrogen peroxide is sold for domestic use
  • 6-10% hydrogen peroxide is used to bleach hair
  • 35% or ‘food-grade’ hydrogen peroxide is used as a cleaning agent (don’t be fooled by the name, ‘food-grade’ definitely doesn’t mean you should drink it!)
  • Up to 90% hydrogen peroxide is in industry

Hazards of Hydrogen Peroxide

As concentrations of hydrogen peroxide vary from around 3% to 90% plus, so the hazards hydrogen peroxide poses also vary.

Low concentration solutions are available over-the-counter, commonly found in brown bottles which block out the light that decomposes the hydrogen peroxide. While some people advocate ingestion, we strongly advise against it. Even a weak solution of hydrogen peroxide can cause harm when ingested, causing irritation to mucous membranes as it decomposes in the stomach. Likewise, coming into contact with hydrogen peroxide even at low concentration can also cause skin and eye irritations.

In its more highly concentrated form that’s used industrially, hydrogen peroxide is considered a hazardous chemical and can be dangerous. It’s a strong oxidiser, is corrosive, can react aggressively in the presence of a reducing agent, and can even explode on contact with organic compounds.

Is Hydrogen Peroxide Bleach?

No, but hydrogen peroxide is an ingredient in bleach. For example, it’s an ingredient in the bleach hairdressers use to dye hair blonde, and it’s also used in many disinfectant products. Chemically, hydrogen peroxide has the empirical formula H2O2 while bleach is commonly a solution of sodium hypochlorite or NaOCl.

Hydrogen Peroxide Specification

Hydrogen Peroxide 6% (20 Vols) – Assay19.7 – 20.3Vols
Hydrogen Peroxide 6% (20 Vols) – Assay5.7 – 6.3% w/v
Hydrogen Peroxide 30% (100 Vols) (General Use) – Assay26.5 – 28.5%
Hydrogen Peroxide 30% (100 Vols) – Assay26.5 – 28.5%
Hydrogen Peroxide 35% – Assay34.8 – 35.6% w/w
Hydrogen Peroxide 35% – AppearanceClear & colourless, free from particles

Hydrogen Peroxide Material Safety Data Sheet (MSDS)

You can find the material safety data sheets for various concentrations of hydrogen peroxide below. These MSDSs list the potential hazards (including health, fire, reactivity and environmental hazards) of hydrogen peroxide and how to use or work with it safely.

Can Hydrogen Peroxide Expire?

Hydrogen peroxide will eventually expire. Once opened, it will last for around six months. Unopened, hydrogen peroxide will expire after about three years.

How Is It Used?

Hydrogen peroxide is a versatile substance with a variety of applications. It is used in a range of industries, especially in bleaching where 60% of the world’s production is used.

Hydrogen peroxide is used in:

  • Bleaching paper, cotton, wood pulp and more
  • Cleaning products like detergents and disinfectants
  • Cosmetics for teeth whitening, bleaching hair and treating acne
  • Glow sticks where it is used to produce chemiluminescence

Hydrogen peroxide is sometimes also used in alternative medicine practices, usually in the treatment of emphysema and even cancer.

However, there is little evidence to support the effectiveness of hydrogen peroxide as a medical treatment. It should also be kept in mind that high strength concentrations or prolonged exposure to the chemical could be fatal.

Flicking through pages of a white book
60% of the world’s hydrogen peroxide production is used in the bleaching industry. Hydrogen peroxide is used to bleach paper, cotton, wood and even hair.

Production of H2O2

There are several manufacturing methods that can be used to produce hydrogen peroxide. The most common method is the anthraquinone process. This involves the reaction of hydrogen (H2) with oxygen (O2) extracted from the air.

Biologically, hydrogen peroxide is formed in most living organisms as a result of biochemical processes. It doesn’t stick around in the body, however, because the enzyme catalase quickly decomposes it into water and oxygen. This is because hydrogen peroxide is toxic to cells.

Hydrogen Peroxide and Bees

Hydrogen peroxide is biologically formed in bees when they convert nectar into honey. When bees carry nectar in their honey stomach, several enzymes are released and added to it. These break it down and eventually help to transform it into honey.

One of these enzymes, glucose oxidase, catalyses the oxidation of glucose whilst the nectar is being carried. This forms hydrogen peroxide and gluconic acid. Because it is unstable, hydrogen peroxide is then decomposed into water and oxygen by the enzyme catalase.

However, there are still trace amounts of hydrogen peroxide in honey, but it’s not necessarily a bad thing. Because of its antibacterial properties, the presence of H2O2 is one of the reasons that honey has an eternal shelf life.

Bees on a honeycomb. Bees produce hydrogen peroxide when making honey.
There are trace amounts of hydrogen peroxide in honey. This is one of the factors that contribute to the immortal powers of honey.

At ReAgent, we supply hydrogen peroxide in a range of concentrations and pack sizes. We also have a 100% quality guarantee on all products so that you buy with confidence. Shop online today or contact us to speak to our team.


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