ASTM D4052-18a: Standard Test Method for Density, Relative Density, and API Gravity of Liquids by Digital Density Meter outlines a test method for determining three qualities of petroleum distillates and viscous oils:
Density: a mass per unit volume at a specified temperature.
Relative Density: the ratio of the density of a material at a stated temperature to the density of water at a stated temperature. Also known as Specific Gravity.
API Gravity: an inverted scale for denoting the “lightness” or “heaviness” of crude oils. It is devised jointly by the American Petroleum Institute (hence, API) and NIST and expressed in degrees API.
A thorough comprehension of these characteristics is important for any material. Density is a fundamental physical property that can be used in conjunction with other properties to characterize both the light and heavy fractions of petroleum and petroleum products. Furthermore, the determination of the density or relative density of petroleum and its products is necessary for the conversion of measured volumes to volumes at the standard temperature of 15°C.
The standard test method outlined in ASTM D4052-18a involves the introduction of a small volume—approximately 1 mL to 2 mL—into an oscillating sample tube. The change in oscillating frequency caused by the change in the mass of the tube is used in conjunction with calibration data to determine the density, relative density, or API Gravity of the sample. The standard document includes both manual and automated injection techniques. Results are obtained by a density meter.
Some products tested by this procedure include gasoline and gasoline-oxygenate blends, diesel, jet, basestocks, waxes, and lubricating oils.
The application of the ASTM D4052-18a test method is restricted to liquids with total vapor pressures (please see ASTM D5191-19: Standard Test Method for Vapor Pressure of Petroleum Products for reference) typically below 100 kPa and viscosities (please see ASTM D445-18: Standard Test Method for Kinematic Viscosity of Transparent and Opaque Liquids or ASTM D7042-16e3: Standard Test Method for Dynamic Viscosity and Density of Liquids by Stabinger Viscometer for reference) typically below about 15,000 mm2/s at the temperature of test.
Please note that ASTM D4052-18a does not cover waxes and highly viscous samples, as they were not a part of the 1999 interlaboratory study (ILS) sample set that was used to determine the current precision statements of the standard method. Users should consult instrument manufacturer instructions for appropriate guidance and precautions when attempting to analyze wax or highly viscous samples.
The specifics of the test method for density, relative density, and API gravity of petroleum products can be found in the ASTM D4052-18a standard.
ASTM D4052-18a: Standard Test Method for Density, Relative Density, and API Gravity of Liquids by Digital Density Meter is available on the ANSI Webstore.