Hydrogen peroxide

Hydrogen peroxide is a mostly clear, blue-ish liquid with similar melting and boiling points to water. It is a powerful and versatile oxidizer, but can act as a reducing agent in some circumstances. It also acts as a very weak acid, forming hydrated peroxide salts (such as sodium peroxide octahydrate) with alkalis in aqueous solution.

Properties

Chemical

Hydrogen peroxide can be used as an oxidizer, and may enhance the oxidizing capabilities on mixing. For example, a mixture of sulfuric acid and hydrogen peroxide will react faster than the acid alone. Hydrogen peroxide is dangerous as it can cause explosions when in contact with combustible materials in high concentration.

Hydrogen peroxide disproportionates into water and oxygen gas. This happens rapidly at high temperatures or when a catalyst, such as Manganese dioxide or Potassium iodide, is added and this is often used to produce oxygen gas in a home chemistry setting.

Physical

Hydrogen peroxide is tinted slightly blue in high concentrations. It has boiling and melting points similar to water, but can be concentrated by fractional crystallization. Concentrations of peroxide 30% and above are considered concentrated.

Availability

Hydrogen peroxide is available readily as a disinfectant in pharmacies and grocery stores, but may only be obtained easily in low concentrations often as 3% or 6% solutions.

Higher concentration peroxide is sold for animal disinfectants, pool/spa treatments, hair bleaching. Some may contain other chemicals, including stabilizers, so read the label first.

Preparation

Hydrogen peroxide can be prepared by reacting concentrated sulfuric acid and barium peroxide.

BaO₂ + H₂SO₄ → H₂O₂ + BaSO₄

The insoluble barium sulfate is filtered from the mixture.

Due to the availability of low concentrations of peroxide worldwide, concentrated hydrogen peroxide solutions are often prepared by evaporating the water from the peroxide, making sure not to boil the solution (as this will break down the peroxide).

Projects

• Make sulfuric acid
• Make peroxides
• Cleaning silver
• Make piranha solution
• Fenton's reagent
• Make copper etching solution
• Singlet oxygen

Handling

Safety

As it is an oxidizer, high concentrations of hydrogen peroxide can ignite or detonate combustible or explosive materials. Lower concentrations are much safer, but regardless of concentration, poisonous.

Storage

Hydrogen peroxide solutions are best stored in cold dark places, such as a fridge. High concentration peroxides are metastable and will slowly build-up pressure, so it's recommended to open the bottles from time to time, to release the pressure.

NEVER store hydrogen peroxide near volatile organic compounds, such as acetone, as there is a risk of forming acetone peroxide.

Disposal

Hydrogen peroxide can be decomposed by adding a catalyst, such as manganese dioxide or iron oxides (ordinary rust will do). This method however should not be used to neutralize concentrated peroxide as the decomposition will generate lots of heat and can lead to explosion. The explosion that crippled the Kursk submarine for example, occured when the peroxide that leaked from a torpedo entered in contact with some rust. It's recommended to not be poured down the drain, as it will quickly decompose in the sewage and may pose an explosion hazard. Adding a sulfide, such as lead(II) sulfide, will result in lead(II) sulfate and water.