Fuel Characterisitics

Vapour Pressure:

It is the pressure exerted by the vapour in equilibrium with the liquid.  Vapor pressure is the quantified description of a liquid’s ability to release vapors.  Atmospheric pressure is a downward force exerted by the atmosphere on the surface of a liquid; the vapor pressure is a measure of the opposing force exerted by the vapor pushing upward from the surface of the liquid. Expressed in mm of Hg @ some Temperature in deg Celcius.

Eg: kerosene has a vapor pressure of 5 mmHg at 100ºF (37.7ºC), which indicates that it will release very little vapor at normal temperatures.

Vapour Density:

Vapor density is a comparative measure with air always having a value of one.  A vapor density less than one indicates the vapor or gas being considered is lighter than air and will tend to rise and dissipate. Vapor density greater than one indicates the vapor or gas being considered is heavier than air and will tend to sink and seek low points.

Specific Gravity:

Specific gravity (also sometimes referred to as specific density) is another relative measure where water is always equal to one. This measure compares the density of a liquid with the density of water. Aspecific gravity of less than one indicates the liquid is lighter than water. A specific gravity greater than one indicates the liquid is heavier than water.

Solubility:

Solubility is the ability of the liquid to combine with water. Solubility is a scale, not a fixed point. Liquids may be insoluble, partially soluble, or completely soluble.  Hydrocarbon liquids, such as gasoline, are not soluble. This information combined with the fact that the specific gravity of gasoline is less than one indicates that gasoline would float on the surface of water and retain its characteristics. Isopropyl alcohol also has a specific gravity less than one but it is soluble, so if it were released into water it would initially float but then form a solution with the water.

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