How is the relative density of a liquid bulk product defined?
The relative density RD of a liquid (formerly also known as “specific gravity”) is defined via the following equation:
RD = ρ / D60
ρ = absolute density of the liquid
D60 = absolute density of water at 60 °F.
The D60 value needs to be known to convert a relative density value into an absolute density value and vice versa.
The D60 value is determined experimentally, and has two values provided via ASTM standards (one valid until 1980, later redefined in 2004):
- ASTM D1250-80: D60 = 999.012 kg/m³
- ASTM D1250-04: D60 = 999.016 kg/m³
The latter is due to changes in the international temperature scale.
Example:
What is the relative density RD of the truck load of gasoline with an absolute density of 800 kg/m³ ?
Solution:
- ASTM D1250-80: RD = 800 kg/m³ / 999.012 kg/m³ = 0.800 791
- ASTM D1250-04: RD = 800 kg/m³ / 999.016 kg/m³ = 0.800 788
(Both values above are rounded to six decimals)
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