DENSITY, RELATIVE DENSITY, AND SPECIFIC GRAVITY
GENERAL
Density is an important property of petroleum products being part of product specifications. Materials are usually bought and sold on that basis or if on volume basis then converted to mass basis via density measurements. This property is almost synonymously termed as density, relative density, gravity, and specific gravity, all terms related to each other. There are at least a dozen test method standards in DO2 manuals that describe this determination. Usually a hydrometer, pycnometer or a more modern digital density meter is used in all these standards. The plurality of the methods is because they are specifically written for different products. Some basic definitions:
Density - The mass (weight in vacuo) of liquid per unit volume at 15° C.
Relative density - The ratio of the mass of a given volume of liquid at 15° C to the mass of an equal volume of pure water at the same temperature.
Specific gravity - Same as relative density.
Real density is obtained when the particle size of the specimen is smaller than 75 μm. It directly influences the physical and chemical properties of the manufactured carbon and graphite artifacts for which it is used.
