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The autoignition temperature or kindling point of a substance is the lowest temperature at which it 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 ignite decreases as the pressure increases or oxygen concentration increases. It is usually applied to a combustible fuel mixture.
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.
Contents |
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
![t_{ig} = \left ( \frac{\pi}{4} \right ) \left (k \rho c \right )\left [ \frac{T_{ig}-T_\infty}{q''} \right]](http://upload.wikimedia.org/math/1/1/3/11351fa94faae9204f93ba5deb901202.png)
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
 |
This section does not cite any references or sources. Please help improve this section by adding citations to reliable sources. Unverifiable material may be challenged and removed. (August 2008) |
- Triethylborane: -20°C (-4°F)
- Silane: <21°C (70°F)
- White phosphorus: 34°C (93°F)
- Carbon disulfide: 90°C (212°F)
- Diethyl ether: 170°C (338°F)
- Diesel: 210°C (410°F)
- Jet A-1: 210°C (410°F)
- Paper: 450°C (842°F)3
- Gasoline (Petrol): 246°C (475°F)
- Magnesium: 473°C (883°F)
- Butane: 500°C (900°F)
- Hydrogen: 571°C (1060°F)
References
- ^ E659 – 78 (Reapproved 2000), "Standard Test Method for Autoignition Temperature of Liquid Chemicals", ASTM, 100 Barr Harbor Drive, West Conshohocken, PA 19428-2959
- ^ Principles of Fire Behavior. ISBN 0-8273-7732-0. 1998.
- ^ "Handbook of Physical Testing of Paper, By Jens Borch, Richard E. Mark, M. Bruce Lyne". Retrieved on 2008-09-08.
- "Handbook of Physical Testing of Paper, By Jens Borch, Richard E. Mark, M. Bruce Lyne". Retrieved on 2008-09-08.
See also
- Pyrolysis
- Flash Point
- Gas burner (For flame temperatures, combustion heat energy values and ignition temperatures)
External links
Wikipedia content modification information:
- This page was last modified on 18 November 2008, at 03:35.
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