Oxidizing properties refer to the ability of a substance to cause or contribute to the combustion of other materials by providing oxygen or other oxidizing elements, even in the absence of air. In the context of a Safety Data Sheet (SDS), oxidizing properties are critical safety characteristics that indicate the potential for a substance to intensify fires or cause combustion of normally non-flammable materials.
Oxidation involves:
Oxidizing properties can be intrinsic to a substance's molecular structure (e.g., presence of certain functional groups) or can arise from specific chemical compositions (e.g., high oxygen content).
Key concepts related to oxidizing properties include:
Information about oxidizing properties in an SDS is critical for several reasons:
Several types of oxidizing substances may be relevant in an SDS:
| Type | Description | Examples |
|---|---|---|
| Oxygen-Rich Inorganic Compounds | Compounds with high oxygen content that can release oxygen when heated or reacted | Perchlorates, chlorates, nitrates, permanganates |
| Peroxides | Compounds containing the peroxide (O-O) bond | Hydrogen peroxide, benzoyl peroxide, organic peroxides |
| Halogens | Elemental halogens that are strong oxidizing agents | Chlorine, bromine, iodine |
| Halogen Oxides and Oxyacids | Compounds containing halogens in high oxidation states | Hypochlorites, chlorine dioxide, perchloric acid |
| Transition Metal Compounds | Compounds containing transition metals in high oxidation states | Chromates, dichromates, manganates |
| Nitro Compounds | Organic compounds containing nitro groups | Nitrobenzene, nitromethane, nitrocellulose |
| Oxidizing Gases | Gases that can cause or contribute to combustion | Oxygen, ozone, nitrous oxide, chlorine |
Under the Globally Harmonized System (GHS), oxidizing substances are classified into several categories based on their physical state and oxidizing power:
| Category | Criteria (UN Test O.1) | Examples |
|---|---|---|
| Category 1 | Mean burning time < mean burning time of 3:2 potassium bromate/cellulose mixture | Potassium permanganate, sodium peroxide |
| Category 2 | Mean burning time ≤ mean burning time of 2:3 potassium bromate/cellulose mixture and criteria for Category 1 not met | Sodium nitrate, potassium dichromate |
| Category 3 | Mean burning time ≤ mean burning time of 3:7 potassium bromate/cellulose mixture and criteria for Categories 1 and 2 not met | Sodium chlorate, some nitrates |
| Category | Criteria (UN Test O.2) | Examples |
|---|---|---|
| Category 1 | Spontaneously ignites when mixed with cellulose in 1:1 ratio, OR mean pressure rise time < mean pressure rise time of 1:1 50% perchloric acid/cellulose mixture | 90% perchloric acid, concentrated nitric acid |
| Category 2 | Mean pressure rise time ≤ mean pressure rise time of 1:1 40% aqueous sodium chlorate/cellulose mixture and criteria for Category 1 not met | 65% nitric acid, 50% hydrogen peroxide |
| Category 3 | Mean pressure rise time ≤ mean pressure rise time of 1:1 65% aqueous nitric acid/cellulose mixture and criteria for Categories 1 and 2 not met | 35% hydrogen peroxide, some nitric acid solutions |
| Category | Criteria | Examples |
|---|---|---|
| Category 1 | Any gas which may, generally by providing oxygen, cause or contribute to the combustion of other material more than air does | Oxygen, nitrous oxide, chlorine, fluorine |
| Test Method | Description | Application |
|---|---|---|
| UN Test O.1 | Measures burning rate of a mixture with cellulose compared to reference mixtures | Oxidizing solids |
| UN Test O.2 | Measures pressure rise time in a mixture with cellulose compared to reference mixtures | Oxidizing liquids |
| UN Test O.3 | Alternative test for oxidizing solids measuring burning rate | Oxidizing solids |
| ISO 10156 | Calculation method based on oxidizing power of gases | Oxidizing gases |
| ASTM D240 | Measures heat of combustion | Supplementary information for oxidizing potential |
| Oxygen Balance Calculation | Theoretical calculation of excess oxygen available for oxidation | Preliminary assessment of oxidizing potential |
| Redox Potential Measurement | Electrochemical measurement of oxidation-reduction potential | Oxidizing power in solution |
A colorless liquid used as a bleaching agent, disinfectant, and oxidizer.
Formula: H₂O₂
GHS Classification: Oxidizing Liquid (Category depends on concentration)
Purple crystalline solid used as a disinfectant, water treatment chemical, and laboratory reagent.
Formula: KMnO₄
GHS Classification: Oxidizing Solid Category 2
White crystalline solid used in fertilizers, food preservation, and pyrotechnics.
Formula: NaNO₃
GHS Classification: Oxidizing Solid Category 3
Colorless to yellow liquid used in fertilizer production, metal etching, and as a laboratory reagent.
Formula: HNO₃
GHS Classification: Oxidizing Liquid (Category depends on concentration)
White crystalline solid used in rocket propellants, fireworks, and explosives.
Formula: NH₄ClO₄
GHS Classification: Oxidizing Solid Category 1
Colorless gas essential for respiration and combustion processes.
Formula: O₂
GHS Classification: Oxidizing Gas Category 1
| Substance | Physical State | GHS Classification | Common Applications |
|---|---|---|---|
| Hydrogen Peroxide (>60%) | Liquid | Oxidizing Liquid Category 1 | Bleaching, disinfection, chemical synthesis |
| Hydrogen Peroxide (35-60%) | Liquid | Oxidizing Liquid Category 2 | Bleaching, disinfection, water treatment |
| Nitric Acid (>65%) | Liquid | Oxidizing Liquid Category 3 | Metal etching, fertilizer production |
| Potassium Permanganate | Solid | Oxidizing Solid Category 2 | Water treatment, disinfection, laboratory reagent |
| Sodium Chlorate | Solid | Oxidizing Solid Category 1 | Herbicide, paper bleaching, pyrotechnics |
| Ammonium Nitrate | Solid | Oxidizing Solid Category 3 | Fertilizer, cold packs, explosives |
| Oxygen | Gas | Oxidizing Gas Category 1 | Medical, welding, industrial processes |
| Chlorine | Gas | Oxidizing Gas Category 1 | Water treatment, bleaching, chemical synthesis |
Oxidizing substances present several significant hazards:
According to GHS and various regional regulations (EU CLP, US OSHA HazCom, etc.), information about oxidizing properties must be provided in Sections 2 and 9 of the Safety Data Sheet. Section 2 includes the hazard classification and associated hazard statements, while Section 9 provides specific physical and chemical properties related to oxidizing potential.
For transportation purposes, oxidizer classification determines the appropriate UN hazard class, division, and packaging requirements under regulations such as ADR, IMDG, and IATA.
In many jurisdictions, the storage and handling of oxidizers are subject to specific regulatory requirements, including quantity limitations, storage compatibility, and fire protection measures.
When reporting oxidizing properties in an SDS: