# Hydrogen peroxide

Hydrogen peroxide identity, aqueous grades, assay and active oxygen bases, conditional physical properties, and source-specific hazard evidence.

Reviewed: 2026-10-30

Tags: chemicals, substances, oxidants

## Identity and solution products

On a mass basis, the **active-oxygen equivalent is about 0.4704 times the H₂O₂ percentage** because the convention counts one oxygen atom per peroxide molecule. Molarity additionally requires solution density for the same concentration and temperature. Hydrogen peroxide is H₂O₂, CAS 7722-84-1, 34.0147 g/mol. [NIST Chemistry WebBook, SRD 69](https://webbook.nist.gov/cgi/cbook.cgi?ID=7722-84-1) [Sigma product information, page 1](https://www.sigmaaldrich.cn/deepweb/assets/sigmaaldrich/product/documents/171/932/216763pis.pdf)

Evonik distinguishes industrial HYPROX from PERTRONIC electronics grades. Nominal concentration does not establish a lot’s trace-element results or stabilizers. [Evonik brochure, pages 16–17](https://products.evonik.com/assets/95/41/Evonik_Hydrogen_Peroxide_Brochure_EN_Asset_2439541.pdf)

## Assay, water, and stabilizers

Sigma-Aldrich product 216763 is described as stabilized ACS reagent with nominal 30 wt.% H₂O₂ and assay 29.0–32.0%. Its public product page lists evaporation residue ≤0.002%, chloride ≤3 ppm, and iron ≤0.5 ppm. These are product specification entries, not measurements from an identified batch. The page does not attach individual analytical methods to these impurity entries. [Sigma-Aldrich 216763, properties](https://www.sigmaaldrich.com/US/en/product/sigald/216763)

The older product-information PDF identifies the assay as redox titration. Its first page carries code 03/03 and lists 0.5 ppm stannate-containing compounds and 1 ppm phosphorus-containing compounds. The second page retains predecessor product H0904 and a 10/07/96 date. Its references attribute the assay to Sigma quality-control data and the stabilizer information to the supplier. These compound-group descriptions do not identify exact molecular additives or their elemental concentrations. [Sigma product information, both pages and references 1 and 4](https://www.sigmaaldrich.cn/deepweb/assets/sigmaaldrich/product/documents/171/932/216763pis.pdf)

Fisher's H325 ACS product page also gives assay 29.0–32.0%. Its U.S. SDS revision 14, dated December 18, 2025, instead lists composition ranges of 20–35 weight% hydrogen peroxide and 65–80 weight% water. The SDS disclaims being a quality specification. Those broader ranges do not replace the assay specification or establish one lot's composition. [Fisher H325 specifications](https://www.fishersci.com/shop/products/hydrogen-peroxide-30-certified-acs-fisher-chemical/p-213406), [Fisher SDS, sections 3 and 16](https://www.fishersci.com/store/msds?countryCode=US&language=en&partNumber=H32530GAL&productDescription=HYDROGEN+PEROXIDE+30+GAL&vendorId=VN00033897)

Synthesis: water is the principal solvent, not an impurity included in the nominal 30% assay. An exact water fraction of 70% follows only for an ideal binary mixture at exactly 30% H₂O₂. The cited documents do not provide a complete additive mass balance or a current lot certificate of analysis.

## Concentration and oxygen-equivalent bases

Mass percent means grams of H₂O₂ per 100 g solution. Molarity means moles per litre of solution. Evonik's table separates mass percent, grams per kilogram, grams per litre, molarity, mole percent, and active oxygen. Footnote 2 assigns its grams-per-litre and molarity entries to 25 °C. [Evonik brochure, page 18](https://products.evonik.com/assets/95/41/Evonik_Hydrogen_Peroxide_Brochure_EN_Asset_2439541.pdf)

Derived chemistry, nonprocedural: the active-oxygen convention counts one oxygen atom per H₂O₂ molecule, approximately 16.00/34.0147 = 0.4704 of its mass. Thus H₂O₂ mass percentage and active-oxygen mass percentage differ by that factor. This is an oxidation-equivalent basis, not a dissolved molecular oxygen fraction. Reduction of peroxide oxygen from oxidation state −1 to −2 represents two moles of electron equivalents per mole H₂O₂, or approximately 17.007 g per mole of electron equivalents. These are stoichiometric definitions, not reaction rates or yields. Evonik lists pure-compound active oxygen as 47.1%. The calculation above gives 47.038486…%, which rounds to 47.0% at one decimal place. The source-listed value and the calculated value remain distinct; the cited table does not explain the discrepancy. [NIST molecular weight](https://webbook.nist.gov/cgi/cbook.cgi?ID=7722-84-1), [Evonik brochure, page 18](https://products.evonik.com/assets/95/41/Evonik_Hydrogen_Peroxide_Brochure_EN_Asset_2439541.pdf)

Derived unit relationship: for H₂O₂ mass fraction w and solution density ρ in g/mL, molarity is 1000ρw/34.0147 mol/L. Density must describe the same composition and temperature as the volume basis. Mass fraction alone cannot determine molarity. Neither active oxygen nor electron equivalents establishes selectivity, process performance, or residual peroxide in another material.

## Physical-property conditions and discrepancies

Evonik's table covers salt-free aqueous solutions. Selected entries illustrate concentration dependence. [Evonik brochure, page 18 and footnote 1](https://products.evonik.com/assets/95/41/Evonik_Hydrogen_Peroxide_Brochure_EN_Asset_2439541.pdf)

| Property | 30 wt.% H₂O₂ | 50 wt.% H₂O₂ | Pure H₂O₂ column |
| --- | --- | --- | --- |
| Density at 20 °C, g/mL | 1.111 | 1.195 | 1.450 |
| Freezing point, °C | −26 | −52 | −0.4 |
| Boiling point at 1013 mbar, °C | 106 | 114 | 150 |

The table supplies no measurement methods or uncertainties for these rows. Pure-compound values cannot describe the 30% solution.

Fisher's H325 SDS lists −33 °C melting point and 108 °C boiling point at 760 mmHg. These differ from Evonik's 30% column. Neither document explains the discrepancy or supplies matching methods. Fisher combines density and specific gravity as 1.11 without a temperature or explicit unit. [Fisher SDS, section 9](https://www.fishersci.com/store/msds?countryCode=US&language=en&partNumber=H32530GAL&productDescription=HYDROGEN+PEROXIDE+30+GAL&vendorId=VN00033897)

Synthesis: these entries remain separate. Their differences do not justify substituting a nearby concentration, averaging values, or treating a phase-transition listing as an operating limit. No decomposition threshold or kinetic model is established here.

## Dated hazard evidence

Fisher's December 2025 U.S. H325 SDS classifies that product as Oxidizing liquids Category 2 and Skin Corrosion Category 1A. Health Canada's assessment, updated in 2025 under Canadian HPR, assigns aqueous hydrogen peroxide Oxidizing Liquids Category 3 at 42.5 to less than 50%, Category 2 at 50 to less than 69.7%, and Category 1 at 69.7% or above, including pure H₂O₂. For the untested subranges above 63.2% but below 69.7%, and above 47.3% but below 50%, Health Canada specifies minimum classifications of Category 2 and Category 3, respectively. Applicable supplier test data supporting a more severe category supersede those minima. The documents give different concentration-classification mappings. The discrepancy remains unresolved here. [Fisher SDS, sections 1–2](https://www.fishersci.com/store/msds?countryCode=US&language=en&partNumber=H32530GAL&productDescription=HYDROGEN+PEROXIDE+30+GAL&vendorId=VN00033897), [Health Canada assessment, Oxidizing Liquids](https://www.canada.ca/en/health-canada/services/environmental-workplace-health/occupational-health-safety/workplace-hazardous-materials-information-system/hazardous-substance-assessments/hydrogen-peroxide.html)

Health Canada describes its assessment as educational and informational. Its oxidizing-liquid discussion cites a 2024 ECHA dossier, and its closing note states that new information can affect classifications. These are dated, regional statements, not a determination of current global legal compliance. Hazard classification also does not establish material compatibility or manufacturing performance. [Health Canada assessment, introductory note, Other information, and footnote 1](https://www.canada.ca/en/health-canada/services/environmental-workplace-health/occupational-health-safety/workplace-hazardous-materials-information-system/hazardous-substance-assessments/hydrogen-peroxide.html)

## Source scope and remaining unknowns

The product webpages show no document revision date. The brochure provides rounded physical data without test methods. The older Sigma sheet's density and pKₐ entries cite handbooks rather than original measurements; those handbooks were not independently reviewed here.

No current lot analysis, complete proprietary stabilizer formulation, original phase-equilibrium dataset, or performance study underlies this page. The evidence does not establish customer capability, a qualified application, or an operating recipe.

Related context: [Surface-finishing processes](../../processes/finishing/index.md).