chem :heating of flammable thg

A flammable liquid catches fire only when the temperature is higher than its ignition point (ignition temperature). For example, the ignition point of ethanol (ethylalcohol) is 365°C, while that of kerosene is 295°C.

Common Bunsen burners used in laboratory can provide a temperature as high as 500-600°C (the flame temperature of a Meker burners can be up to 1100-1200°C). This temperature is higher than the ignition points of many common flammable liquids used in laboratory. When direct heating such a flammable liquid intest tube using a Bunsen burner, the vapour that escapes from the open end of the test tube may be ignited by the Bunsen flame. There is a risk of fire.

To solve the problem, the flammable liquid would be heated by a water bath.Under such circumstances, the open end is far apart from the Burner flames, and they are separated by the set-up of heating. Furthermore, the temperature of water bath (100°C) is too low to ignite the vapour. It is much safer.