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Encyclopedia > Dinitrogen tetroxide
Dinitrogen tetroxide
Dinitrogen tetroxide
Dinitrogen tetroxide
Systematic name Dinitrogen Tetroxide
Chemical formula N2O4
Molecular weight 92.011 u
Appearance  ?
CAS number 10544-72-6
MSDS link Air Liquide MSDS (PDF)
Physical properties
Density 1443 kg/m³ (liquid at 1.013 bar, boiling point)
Solubility reacts with water
Thermal decomposition maintains equilibrium with
NO2 at room temperature
Solid properties
Standard enthalpy change of formation
 ? kJ/mol
Standard molar entropy
 ? J/(mol•K)
Heat capacity
 ? J/(mol•K)
Density  ? g/cm3
Liquid properties
ΔfH0liquid -19.5 kJ/mol
S0liquid 209.2 J/(mol•K)
Cp 142.7 J/(mol•K)
Density 1.44 g/cm3
Gas properties
ΔfH0gas 11.1 kJ/mol
S0gas 304.4 J/(mol•K)
Cp 79.2 J/(mol•K)
Phase behavior
Melting point 261.9 K (-11.2 °C)
Boiling point 294.3 K (21.1 °C)
Triple point  ? K (? °C)
 ? kPa
Critical point 430.9 K (157.8 °C)
10.132 MPa
Vapor pressure 96 kPa (20 °C) [1] (?)
Heat of fusion
14.67 kJ/mol [2] (?)
Entropy of fusion
 ? J/mol•K
Heat of vaporization
39.60 kJ/mol [3] (?)
Ingestion  ?
Inhalation Corrosive & toxic
Skin Corrosive
Eyes Corrosive
OSHA Permissible Exposure Limit
5 ppm
NIOSH Immediate Danger to Life and Health
20 ppm
Personal protection
Skin: Prevent skin contact
Eyes: Prevent eye contact
Wash skin: When contaminated
Remove: When wet or contaminated
Change: No recommendation
Provide: Eyewash, Quick drench
Reacts with
combustible material
water (to form nitric acid)
chlorinated hydrocarbons
carbon disulfide
Except where noted otherwise, data are given for
materials in their standard state (at 25°C, 100 kPa)
Infobox disclaimer and references

Nitrogen tetroxide (or dinitrogen tetroxide) is the chemical compound N2O4. It is a powerful oxidizer, and is highly toxic and corrosive. N2O4 has received much attention as a rocket fuel. It is useful reagent in chemical synthesis. Image File history File links Download high resolution version (1100x948, 199 KB) File links The following pages on the English Wikipedia link to this file (pages on other projects are not listed): Dinitrogen tetroxide Nitrogen oxide User:Benjah-bmm27/Gallery User:Ben Mills/Gallery ... IUPAC nomenclature is a system of naming chemical compounds and of describing the science of chemistry in general. ... A chemical formula (also called molecular formula) is a concise way of expressing information about the atoms that constitute a particular chemical compound. ... The molecular mass of a substance (less accurately called molecular weight and abbreviated as MW) is the mass of one molecule of that substance, relative to the unified atomic mass unit u (equal to 1/12 the mass of one atom of carbon-12). ... The unified atomic mass unit (u), or dalton (Da), is a small unit of mass used to express atomic and molecular masses. ... CAS registry numbers are unique numerical identifiers for chemical compounds, polymers, biological sequences and alloys. ... This page meets Wikipedias criteria for speedy deletion. ... Density (symbol: ρ - Greek: rho) is a measure of mass per unit of volume. ... Kilogram per cubic metre is the SI measure of density and is represented as kg/m³, where kg stands for kilogram and m³ stands for cubic metre. ... The bar (symbol bar) and the millibar (symbol mbar, also mb) are units of pressure. ... A substance is soluble in a fluid if it dissolves in that fluid. ... In jewelry, a solid gold piece is the alternative to gold-filled or gold-plated jewelry. ... The standard enthalpy of formation or standard heat of formation of a compound is the change of enthalpy that accompanies the formation of 1 mole of a substance in its standard state from its constituent elements in their standard states (the most stable form of the element at 1 atmosphere... In chemistry, the standard molar entropy is the entropy content of one mole of substance, under conditions of standard temperature and pressure. ... To meet Wikipedias quality standards, this article or section may require cleanup. ... A liquid will assume the shape of its container. ... A gas is one of the four main phases of matter (after solid and liquid, and followed by plasma), that subsequently appear as a solid material is subjected to increasingly higher temperatures. ... The melting point of a solid is the temperature at which it changes state from solid to liquid. ... The kelvin (symbol: K) is the SI unit of temperature, and is one of the seven SI base units. ... A degree Celsius (°C) is a unit of temperature named after the Swedish astronomer Anders Celsius (1701-1744), who first proposed a similar system in 1742. ... The boiling point of a substance is the temperature at which it can change its state from a liquid to a gas throughout the bulk of the liquid at a given pressure. ... In physics, the triple point of a substance is the temperature and pressure at which three phases (gas, liquid, and solid) of that substance may coexist in thermodynamic equilibrium. ... The pascal (symbol Pa) is the SI unit of pressure. ... The term critical point can mean any of: critical point (thermodynamics) critical point (mathematics) critical loops (topology) critical point (set theory) This is a disambiguation page: a list of articles associated with the same title. ... The megapascal, symbol MPa is an SI unit of pressure. ... Vapor pressure is the pressure of a vapor in equilibrium with its non-vapor phases. ... Wikipedia does not yet have an article with this exact name. ... Heat of fusion is the amount of heat energy which must be absorbed or lost for 1 gram of a substance to change states from a solid to a liquid or vice versa. ... A kilojoule (abbreviation: kJ) is a unit of energy equal to 1000 joules. ... The mole and its simple conversions into different units of measurements. ... The Entropy of fusion of a substance represents the increase in the degree of disorder involved in the transition from an organized crystalline solid to the disorganized structure of a liquid. ... The joule (symbol: J) is the SI unit of energy, or work with base units of kg·m²/s² (N·m). ... The heat of vaporization is a physical property of substances. ... If you are searching for the organization, click OSHA. Osha (Ligusticum porteri) is a perennial herb used for its medicinal properties. ... The Permissible Exposure Limit (PEL or OSHA PEL) is a legal limit in the United States for personal exposure to a substance, usually expressed in parts per million (ppm). ... Parts per million (ppm) is a measure of concentration that is used where low levels of concentration are significant. ... The National Institute for Occupational Safety and Health (NIOSH) is the United States federal agency responsible for conducting research and making recommendations for the prevention of work-related injury and illness. ... Immediately Dangerous to Life and Health (IDLH or NIOSH IDLH) is a limit for personal exposure to a substance defined by the United States National Institute for Occupational Safety and Health (NIOSH), normally expressed in parts per million (ppm). ... In chemistry, the standard state of a material is its state at 1 bar (100 kilopascals) and 25 degrees Celsius (298. ... A chemical compound is a chemical substance formed from two or more elements, with a fixed ratio determining the composition. ... An oxidizing agent is a substance that oxidizes another substance in electrochemistry or redox chemical reactions in general. ...


Structure and properties

The molecule is planar with an N-N bond distance of 1.78 Å and N-O distances of 1.19 Å. Unlike NO2, N2O4 is diamagnetic.[1] It is also colorless but can appear brownish yellow liquid due to the presence of NO2 according to the following equilibrium: Diamagnetism is a very weak form of magnetism that is only exhibited in the presence of an external magnetic field. ...

N2O4 → 2 NO2

Higher temperatures push the equilibrium towards nitrogen dioxide. Inevitably, some nitrogen tetroxide is a component of smog containing nitrogen dioxide. Victorian London was notorious for its thick smogs, or pea-soupers, a fact that is often recreated to add an air of mystery to a period costume drama. ...


Nitrogen dioxide is made by the catalytic oxidation of ammonia: steam is used as a diluent to reduce the combustion temperature. Most of the water is condensed out, and the gases are further cooled; the nitric oxide that was produced is oxidised to nitrogen dioxide, and the remainder of the water is removed as nitric acid. The gas is essentially pure nitrogen tetroxide, which is condensed in a brine-cooled liquefier. In chemistry and biology, catalysis (in Greek meaning to annul) is the acceleration of the rate of a chemical reaction by means of a substance, called a catalyst, that is itself unchanged chemically by the overall reaction. ... The most fundamental reactions in chemistry are the redox processes. ... Ammonia is a compound of nitrogen and hydrogen with the formula NH3. ... The chemical compound nitric oxide is a gas with chemical formula NO. It is an important signaling molecule in the body of mammals including humans, one of the few gaseous signaling molecules known. ... [1] R-phrases , S-phrases , , , , , Supplementary data page Structure and properties n, εr, etc. ... The chemical compound nitric acid (HNO3), otherwise known as aqua fortis or spirit of nitre, is a colorless, corrosive liquid, a toxic acid which can cause severe burns. ...

Use as a rocket fuel

Dinitrogen tetroxide is one of the most important rocket propellants ever developed and by the late 1950s it became the storable oxidizer of choice for rockets in both the USA and USSR. It is a hypergolic propellant often used in combination with a hydrazine-based rocket fuel. One of the earliest uses of this combination was on the Titan rockets used originally as ICBM's and then as launch-vehicles for many spacecraft. Used on the U.S. Gemini and Apollo spacecraft, it continues to be used on the Space Shuttle, most geo-stationary satellites and many deep-space probes. It now seems likely that NASA will continue to use this oxidiser in the next-generation 'crew-vehicles' which will replace the shuttle. The 1950s were the decade that traditionally speaking, spanned the years 1950 through 1959. ... Hypergolic rocket fuels spontaneously ignite when their two components come into contact with each other. ... A propellant is a material that is used to move an object by applying a motive force. ... Hydrazine is a chemical compound with formula N2H4 used as a rocket fuel. ... A Redstone rocket, part of the Mercury program The traditional definition of a rocket is a vehicle, missile or aircraft which obtains thrust by the reaction to the ejection of fast moving fluid from within a rocket engine. ... Fuel is a material with one type of energy which can be transformed into another usable energy. ... Titan is a family of U.S. expendable rockets. ...

When used as a propellant, dinitrogen tetroxide is usually referred to simply as 'Nitrogen Tetroxide' and the acronym 'NTO' is extensively used. Additionally, NTO is often used with the addition of a small percentage of nitric oxide, which inhibits stress-corrosion cracking of titanium alloys, and in this form, propellant-grade NTO is referred to as "Mixed Oxides of Nitrogen" or "MON".Most spacecraft now use MON instead of NTO, for example, the Space Shuttle flies with MON3 (NTO containing 3wt%NO). [4]

Power generation using N2O4

The tendency of N2O4 to reversibly break into NO2 has lead to research into its use in advanced power generation systems as a so-called dissociating gas. "Cool" nitrogen tetroxide is compressed and heated, causing it to dissociate into nitrogen dioxide at half the molecular weight. This hot nitrogen dioxide is expanded through a turbine, cooling it and lowering the pressure, and then cooled further in a heat sink, causing it to recombine into nitrogen tetroxide at the original molecular weight. It is then much easier to compress to start the entire cycle again. Such dissociative gas Brayton Cycles have the potential to considerably increase efficiencies of power conversion equipment.

Chemical reactions

N2O4 has a very rich chemistry.[2]

Intermediate in the manufacture of nitric acid

Nitric acid is manufactured on a large scale via N2O4. This species reacts with water to give both nitrous acid and nitric acid: Nitrous acid (molecular formula HNO2) is a weak monobasic acid known only in solution and in the form of nitrite salts. ... The chemical compound nitric acid (HNO3), otherwise known as aqua fortis or spirit of nitre, is a colorless, corrosive liquid, a toxic acid which can cause severe burns. ...

N2O4 + H2O → HNO2 + HNO3

The coproduct HNO2 upon heating disproportionates to NO and more nitric acid. Disproportionate may mean: Not in fair or equal terms; see proportionality. ... The chemical compound nitric oxide is a gas with chemical formula NO. It is an important signaling molecule in the body of mammals including humans, one of the few gaseous signaling molecules known. ...

Synthesis of metal nitrates

N2O4 behaves as the salt [NO+][NO3-], the former being a strong oxidant:

2 N2O4 + M → 2 NO + M(NO3)2

(M = Cu, Zn, Sn). N2O4 see: NOBF4 The structure of the nitrosonium ion The nitrosonium ion is NO+, the nitrogen atom is bonded to an oxygen atom with a bond order of 2, the overall diatomic species bearing a positive charge. ...

External links

  • National Pollutant Inventory - Oxides of nitrogen fact sheet
  • NIOSH Pocket Guide to Chemical Hazards: Nitrogen tetroxide
  • Air Liquide Gas Encyclopedia: NO2 / N2O4
  • Link page to external chemical sources.


  1. ^ Holleman, A. F.; Wiberg, E. "Inorganic Chemistry" Academic Press: San Diego, 2001. ISBN 0-12-352651-5.
  2. ^ Addison, C. C. (1980). "Dinitrogen Tetroxide, Nitric Acid, and Their Mixtures as Media for Inorganic Reactions". Chemical Reviews 80: 21-39. DOI:10.1021/cr60323a002.

  Results from FactBites:
Artemis Project: Lunar Dinitrogen Tetroxide Production (1333 words)
However, dinitrogen tetroxide is 69.6% oxygen, which can be readily extracted from lunar minerals, and indeed a lunar oxygen extraction pilot plant will be carried on the first mission.
If a simple apparatus was included to synthesize dinitrogen tetroxide out of imported ammonia and indiginous oxygen, it would afford considerable leveraging towards the cost of future missions.
Dinitrogen tetroxide can be prepared by thermal decomposition of heavy metal nitrates, or by reducing or decomposing nitric acid.
  More results at FactBites »



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