Dinitrogen tetroxide

Dinitrogen tetroxide (N₂O₄) is a colorless molecular compound in equilibrium with brown nitrogen dioxide (NO₂). It is used as a storable liquid oxidizer in rocket propulsion.

Nitrogen dioxide: Nitrogen dioxide (NO₂) is a reactive, brown gas and radical that dimerizes to form dinitrogen tetroxide. It is the monomer in the reversible equilibrium that gives N₂O₄ its temperature-dependent color.
Hypergolic propellant: A hypergolic propellant ignites spontaneously when its fuel and oxidizer come into contact. N₂O₄ ignites on contact with fuels such as hydrazine, eliminating a separate ignition system.
Antoine Lavoisier: Antoine Lavoisier was an eighteenth-century French chemist who helped establish modern chemical nomenclature and conservation of mass. His oxygen-based account of acids shaped early interpretations of nitrogen oxides.
Nitrous oxide: Nitrous oxide (N₂O) is a colorless gas used as an anesthetic and oxidizer, with nitrogen in a different oxidation state. Its formula and reactivity differ sharply from those of N₂O₄ despite the similar name.
Chemical equilibrium: Chemical equilibrium is the dynamic state in which forward and reverse reactions occur at equal rates. The balance between N₂O₄ and NO₂ shifts with temperature and pressure.
Aerozine 50: Aerozine 50 is a 50:50 by mass blend of hydrazine and unsymmetrical dimethylhydrazine used as rocket fuel. This fuel was paired with N₂O₄ in several launch vehicles and spacecraft.
Joseph Louis Gay-Lussac: Joseph Louis Gay-Lussac was a French chemist known for work on gases and the laws of combining volumes. His studies of nitrogen oxides helped establish their distinct chemical compositions.
Nitric oxide: Nitric oxide (NO) is a colorless, reactive radical gas that readily reacts with oxygen to form nitrogen dioxide. Unlike N₂O₄, it is a monomeric radical rather than a dimeric reservoir of NO₂.
Le Châtelier's principle: Le Châtelier's principle predicts how an equilibrium responds to changes in conditions such as temperature or pressure. It predicts how heating or compression changes the NO₂–N₂O₄ mixture.
Titan II: Titan II was a United States intercontinental ballistic missile and space-launch vehicle powered by storable liquid propellants. Its first and second stages used Aerozine 50 fuel with N₂O₄ oxidizer.

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Unsymmetrical dimethylhydrazineRelated: It is a common oxidizer paired with UDMH-based fuels in hypergolic engines.