The autoignition temperature, or the ignition temperature of a substance is the lowest temperature at which a chemical will spontaneously ignite in a normal atmosphere, without an external source of ignition, such as a flame or spark. This temperature is required to supply the activation energy needed for combustion. The temperature at which a chemical will detonate decreases as the pressure increases or oxygen concentration increases. It is usually applied to a combustible fuel mixture. Spontaneous combustion can have several meanings: The self-ignition, or apparent self-ignition, and burning of any mass; often of highly flammable materials, such as a pile of oily rags; see combustion. ... The sparks generated by striking steel against a flint provide the activation energy to initiate combustion in this Bunsen burner. ... Combustion or burning is a complex sequence of chemical reactions between a fuel and an oxidant accompanied by the production of heat or both heat and light in the form of either a glow or flames. ...

Autoignition temperatures of liquid chemicals are typically measured using a 500 mL flask placed in a temperature controlled oven in accordance with the procedure described in ASTM E659 ^[1]. The commonly accepted autoignition temperature of paper, 451 °F (233 °C), is well known because of the popular novel Fahrenheit 451 by author Ray Bradbury (although the actual autoignition temperature depends on the type of pulp used in the paper's manufacture, chemical content, paper thickness, etc.) Piece of Letter paper Paper is a thin material produced by the amalgamation of plant fibres, which are subsequently held together without extra binder, largely by hydrogen bonds and fiber entanglement. ... Fahrenheit is a temperature scale named after the German physicist Daniel Gabriel Fahrenheit (1686–1736), who proposed it in 1724. ... Celsius relates to the Celsius or centrigrade temperature scale. ... This article is about the novel. ... Ray Douglas Bradbury (born August 22, 1920) is an American fantasy, horror, science fiction, and mystery writer best known for The Martian Chronicles, a 1950 book which has been described both as a short story collection and a novel, and his 1953 dystopian novel Fahrenheit 451. ...

Autoignition equation

The time it takes for a material to reach its autoignition temperature when exposed to a heat flux is given by the following equation

^[2]

where k = thermal conductivity (W/(m·K)), ρ = density (kg/m³), and c = specific heat capacity (J/(kg·K)) of the material of interest. is the temperature, in kelvins, the material starts at (or the temperature of the bulk material), and q″ is the heat flux (W/m²) incident to the material.

Autoignition point of selected substances

• Triethylborane: -20 °C (-4 °F)
• Silane: <21 °C (70 °F)
• White phosphorus: 34 °C (93 °F)
• Carbon disulfide: 100 °C (212 °F)
• Gasoline: 257 °C (495 °F)
• n-Butane: 282 °C (540 °F)
• Magnesium: 473 °C (883 °F)
• Butane: 500 °C (900 °F)
• Hydrogen: 571 °C (1060 °F)

See Organoboranes TEB - Triethylborane was used to ignite the JP-7 fuel of the Pratt & Whitney J-58 ramjet engines powering the Lockheed SR-71 Blackbird spy plane. ... Silane is a chemical compound with chemical formula SiH4. ... This article is about the chemical element. ... Carbon disulfide (CS2) is a colorless liquid with a pleasant odor that is like the smell of chloroform. ... Gasoline, also called petrol, is a petroleum-derived liquid mixture consisting mostly of hydrocarbons and enhanced with benzene or iso-octane to increase octane ratings, used as fuel in internal combustion engines. ... R-phrases S-phrases , , Flash point −60 °C Autoignition temperature 287 °C Explosive limits 1. ... General Name, Symbol, Number magnesium, Mg, 12 Chemical series alkaline earth metals Group, Period, Block 2, 3, s Appearance silvery white Atomic mass 24. ... Butane, also called n-butane, is the unbranched alkane with four carbon atoms, CH3CH2CH2CH3. ... General Name, Symbol, Number hydrogen, H, 1 Chemical series nonmetals Group, Period, Block 1, 1, s Appearance colorless Atomic mass 1. ...

References

1. ^ E659 – 78 (Reapproved 2000), “Standard Test Method for Autoignition Temperature of Liquid Chemicals,” ASTM, 100 Barr Harbor Drive, West Conshohocken, PA 19428-2959
2. ^ Principles of Fire Behavior. ISBN 0-8273-7732-0. 1998.

Further reading

• Analysis of Effective Thermal Properties of Thermally Thick Materials.http://www.fire.nist.gov/bfrlpubs/fire03/art015.html

See also

• Pyrolysis
• Flash Point
• Gas burner (For Flame Temperatures, Combustion heat energy values and ignition temperatures)