Density' has largely replaced 'Relative Density' or 'Specific Gravity', which is the ratio of the mass of a given volume of liquid at one temperature, to the mass of an equal volume of pure water at the same or another temperature. Density is normally physically measured at higher temperatures, and is then corrected to the standard temperature of 15 Deg C using ASTM tables. This is an indicator of the ignition quality calculated using the relative density and aniline point. It is applicable to distillate grades only, and cannot be used for residual fuels. This is the term used to describe any of the wide range of products produced by distillation, as distinct from bottoms, cracked stock, and natural gas liquids.
Distillate products have a 'mid-boiling range,' and include gas oil and kerosene.
Distillate fuels are also sometimes called Middle Distillates or Distillate Fuels. The flash point limit is set as a safeguard against fire and is the only parameter of a marine fuel which has a legal significance. Unlike other parameters of marine fuels, where from time to time exceptions may be granted from meeting certain specification limiting values, with flash point there can be no exceptions to meeting the 60 Deg C minimum specification under any circumstances whatsoever. If a marine fuel is found to have a flash point below 60 Deg C, the flash point cannot be raised by mixing the fuel with another fuel having a higher flash point. This is because the mixing relationship is not linear, and it only takes a small amount of light volatile vapor in the lower flash point fuel to significantly lower the flash point of the higher flash point fuel.