Kerosene oil is used in lamps for illumination purpose. The burning oil should not be sufficiently volatile at ordinary temperatures, otherwise it's vapour would form explosive mixture with air and thus making its use lamps a source of danger.
Just a lighted match- strike or a smouldering cigarette end if thrown into the oil godown might put the whole stock be in used which do not give enough vapours at a certain minimum temperature.
This temputure which is commonly known as Flash Point or the Ignition Temperature may be defined as :
The minimum temperature at which an oil gives off enough vapours to form a momentary flash of light when a naked flame is brought near its surface.
The ignition temperature of an oil depends on the proportion of volatile hydrocarbons present in it. An oil cold climates must necessarily be 'low boiling' and the one used in tropical climates must be 'high boiling'
Thus the flash point fixed in cold countries is low, while in not countries it is high.
Determination of Flash point:- The flash point oils is usually detetrmined by means of Abel's Apparatus a modified. A beaker is fitted with a cork having a big hole in its centre. A thermometer 🌡️ and cork so that their tips are about 5- 10 mm apart just above the oil surface.
The bulb of the thermometer should be kept dipped in the oil. The beaker containing the whole arrangement is then fixed in a central cork is covered with a watch glass or a thin glass plate.
The temperature of the bath is now gradually raised and sparks are sent across the electrodes by connecting them with an induction coil and accumulator. Just when the temperature of the watch, glass 🥂 or the plate is lifted by an explosion.
The temperature shown by inner thermometer at this point is recorded.
