API gravity: Difference between revisions

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The [[American Petroleum Institute]] gravity, or '''API gravity''', is a measure of how heavy or light a [[petroleum]] liquid is compared to water: if its API gravity is greater than 10, it is lighter and floats on water; if less than 10, it is heavier and sinks.

API gravity is thus an inverse measure of a petroleum liquid's [[density]] relative to that of water (also known as [[specific gravity]]). It is used to compare densities of [[List of crude oil products|petroleum liquids]]. For example, if one petroleum liquid is less dense than another, it has a greater API gravity. Although mathematically, API gravity is mathematically a [[dimensionless quantity]], (see the formula below), it is referred to as being in 'degrees'. API gravity is graduated in degrees on a [[hydrometer]] instrument. API gravity values of most petroleum liquids fall between 10 and 70 degrees.

==History of development==