Relative density

Relative density (also known as specific gravity) is a measure of the density of a material. It is dimensionless, equal to the density of the material divided by the density of water (or, sometimes used for gases, of air).

Related Topics:
Density - Dimensionless - Water - Air

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Since water's density is 1.0 × 103 kg/m3 in SI units, the relative density of a material is approximately the density of the material measured in kg / m3 divided by 1000 (the density of water). There are no units of measurement.

Related Topics:
Kg - M³ - SI

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Water's density can also be measured as nearly one gram per cubic centimetre (at maximum density) in metric units. The relative density therefore has nearly the same value as density of the material expressed in grams per cubic centimetre, but without any units of measurement.

Related Topics:
Gram - Cubic centimetre - Units of measurement

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Relative density or specific gravity are often ambiguous terms. This quantity is often stated for a certain temperature. Sometimes when this is done, it is a comparison of the density of the commodity being measured at that temperature, with the density of water at the same temperature. But they are also often compared to water at a different temperature.

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Relative density is often expressed in forms similar to this:

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:relative density: 8.15_{mbox{4 C}}^{mbox{20 C}} ,, or specific gravity: 2.432_0^{15}

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The superscripts indicate the temperature at which the density of the material is measured, and the subscripts indicate the temperature of the water to which it is compared.

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Density of water calculated from formula in 68th CRC Handbook of Chemistry and Physics 1987–1988.

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