Focal point (chemistry)
The focal point of a substance is the temperature at which its vapor pressure is so high that the resulting gas - air mixture can be ignited with an ignition source , and combustion continues when the ignition source is removed. Most of the time, the substance to be ignited is already in the form of a liquid .
If the flammable liquid has a temperature lower than the flash point , the liquid cannot be ignited with an ignition source. Only when the temperature of the flash point is reached does the liquid form a sufficient quantity of flammable vapors which can ignite. However, the amount of steam flowing in is not large enough to enable permanent combustion when the ignition source is removed again. Only when the focal point, which is usually only a few Kelvin higher, is reached, is the amount of steam formed sufficient to enable permanent combustion.
From a safety point of view, the flash point is far more important than the fire point, since even at the lower flash point temperature, explosive gas-air mixtures can ignite. The resulting heat of combustion is not sufficient to heat the liquid until it reaches the fire point.
Individual evidence
- ^ Brockhaus ABC Chemie , VEB FA Brockhaus Verlag Leipzig 1965, p. 201.
Web links
- Experiments with Fire (accessed April 6, 2020)
- Alcohol, Ethanol (accessed April 6, 2020)