API gravity

Investigation by the U.S. National Academy of Sciences found major errors in salinity and temperature controls that had caused serious variations in published values.

[5] This method is based on the principle of buoyancy and utilizes a specially calibrated hydrometer to determine the API gravity of a liquid sample.

[6] The procedure typically involves the following steps: The hydrometer method is widely used due to its simplicity and low cost.

However, it requires a relatively large sample volume and may not be suitable for highly viscous or opaque fluids.

[7] Proper cleaning and handling of the hydrometer are crucial to maintain accuracy, and for volatile liquids, special precautions may be necessary to prevent evaporation during measurement.

[8] Crude oil is classified as light, medium, or heavy according to its measured API gravity.

Bitumen derived from oil sands deposits in Alberta, Canada, has an API gravity of around 8°.