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Hydrogen peroxide

physical science Maturity 7-9 Next article →

Hydrogen peroxide is a chemical compound with the molecular formula H2O2. It is the simplest peroxide, meaning it contains an oxygen-oxygen single bond. In its pure form, the substance is a very pale blue liquid. However, most people encounter it as a colorless liquid because it is usually diluted in water. This compound is highly reactive and serves as an important oxidizer and bleaching agent.

Hydrogen Peroxide Bottle
Hydrogen Peroxide Bottle

It is also widely used as an antiseptic for cleaning. Because it is so reactive, it must be handled with great care depending on its concentration.

The molecule of hydrogen peroxide is asymmetrical and highly polarized. This means its electrical charge is not spread evenly across the molecule. It also has a strong tendency to form hydrogen bond networks. These networks make the liquid more viscous, or thicker, than pure water. The shape of the molecule is nonplanar, which means it is not flat. Instead, it has a twisted, C2 symmetry.

Riedl-Pfleiderer process
Riedl-Pfleiderer process

This specific shape was first proven by Paul-Antoine Giguère in 1950 using infrared spectroscopy. The molecule is also chiral, meaning it exists in two different forms that are mirror images of each other. In fact, it is the smallest molecule to show this property, known as enantiomerism.

Hydrogen peroxide can exist in many different concentrations. For household use, consumers usually buy solutions that are 3% to 6% by weight in water. Laboratories often use a 30% concentration for their experiments. Industrial grades can range from 70% to 98%. These high concentrations are much more hazardous. If a solution is above 68%, it can convert entirely into steam and oxygen. This process can cause the temperature of the steam to increase. Because of this risk, concentrated hydrogen peroxide is sometimes called "high-test peroxide."

Hydrogen peroxide 35 percent on skin
Hydrogen peroxide 35 percent on skin

It is so energetic that it can be used as a monopropellant or an oxidizer in rocketry.

Rocket Belt Propulsion
Rocket Belt Propulsion

The history of discovering and making hydrogen peroxide is quite long. In 1799, Alexander von Humboldt may have reported the first synthetic peroxide, though his wording was unclear. In 1819, Louis Jacques Thénard identified a compound he called "oxygenated water," which we now know as hydrogen peroxide. In 1892, the Italian chemist Giacomo Carrara determined its molecular mass. He used a method called freezing-point depression to find this value.

Phase diagram hydrogen peroxide water
Phase diagram hydrogen peroxide water

Later, the anthraquinone process was developed in the 1930s by the German manufacturer IG Farben. This method remains the primary way we manufacture the chemical today.

Modern production relies almost entirely on the anthraquinone process. This is a catalytic cycle that recycles materials to create the compound efficiently.

Riedl-Pfleiderer process
Riedl-Pfleiderer process

First, an anthraquinone is reduced using hydrogen on a palladium catalyst. This turns it into anthrahydroquinone. Next, the anthrahydroquinone undergoes autoxidation when it meets oxygen. The hydrogen atoms transfer to the oxygen molecule, which produces hydrogen peroxide and regenerates the original anthraquinone. This cycle allows manufacturers to reuse the expensive quinone and the catalyst.

Container JOTU501003 9
Container JOTU501003 9

This efficient method has allowed global production to grow massively over the last century.

Production numbers show how important this chemical has become to the world. In 1950, the annual production was only 35,000 tonnes. By 1970, that number rose to 300,000 tonnes. By 1998, production reached 2.7 million tonnes. In 2006, the world produced about 2.2 million tonnes.

HydrogenPeroxideTankCarBoltonON
HydrogenPeroxideTankCarBoltonON

Most of this was sold at concentrations of 70% or less. Large amounts are also moved around the world using specialized equipment like ISO tank containers and rail tank cars.

Container JOTU501003 9
Container JOTU501003 9
HydrogenPeroxideTankCarBoltonON
HydrogenPeroxideTankCarBoltonON

Hydrogen peroxide is also a natural part of our world. It is found in biological systems, including the human body. In nature, enzymes called peroxidases help to manage or decompose it. It also exists in the environment, such as in surface water and groundwater. It can even form in the atmosphere when water is exposed to UV light.

Ascaridol
Ascaridol

In the ocean, sea water contains between 0.5 and 14 micrograms per liter of the substance. In freshwater, the concentration is between 1 and 30 micrograms per liter. These small amounts show that hydrogen peroxide is a constant, active part of the Earth's natural chemistry.

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🖼️ Images & Media (11)
File:Phase diagram hydrogen peroxide water.svg
Phase diagram hydrogen peroxide water.svg
File:Riedl-Pfleiderer process.svg
Riedl-Pfleiderer process.svg
File:Container JOTU501003 9.jpg
Container JOTU501003 9.jpg
File:HydrogenPeroxideTankCarBoltonON.jpg
HydrogenPeroxideTankCarBoltonON.jpg
File:Ascaridol.svg
Ascaridol.svg
File:Pheropsophus verticalis 01 Pengo.jpg
Pheropsophus verticalis 01 Pengo.jpg
File:Rocket Belt Propulsion.svg
Rocket Belt Propulsion.svg
File:Contact lens case for Hydrogen Peroxide solution showing bubbles.jpg
Contact lens case for Hydrogen Peroxide...
File:Chemiluminescance.JPG
Chemiluminescance.JPG
File:Hydrogen peroxide 35 percent on skin.jpg
Hydrogen peroxide 35 percent on skin.jpg
File:Hydrogen Peroxide Bottle.jpg
Hydrogen Peroxide Bottle.jpg
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