Relative density

The Relative density d, and specific gravity is the ratio of two densities.

• The ratio of the density ρ of a substance to the density ρ0 of a standard state of this substance
• The density ρ of a substance to the reference density ρ0 a reference substance

The relative density is a size ratio that is a dimensionless quantity without a unit. The density itself is mass per volume (unit: kg / m³). Definition see DIN 1306.

Reference values

Common standard reference densities (Normal) is the density of pure water at STP 3.98 ° C and the density of dry air at normal conditions (0 ° C and 1013.25 mbar = 1.2931 kg / m³ ) or standard condition ( 20 ° C or 25 ° C at the same air pressure).

The relative density is the ratio of the mass of a volume of a liquid at the temperature T1 to the mass of same volume of water at the temperature T2. A common relative density is, so this describes the density of a liquid at 20 ° C in (eg, 2 g / cm ³) in relation to the density of water at 20 ° C (about 1 g / cm ³). The relative density would be 2, thus, the liquid at 20 ° C, is twice as dense as water at 20 ° C. Another example is, this describes the density of a liquid at 20 ° C in relation to the density of water at 4 ° C.

Use

In mineralogy and engineering values ​​indicated are generally related to the density of water. The use is useful when a material is present in various structures, for example, with greater or lesser porosity, for example, due to different temperatures.

For gases it is usually used to represent the " severity ratio " to air. See DIN 1871 ( May 1999), in which the relative density of a gas is defined as the quotient of the density of a gas and the density of dry air at the same pressure and temperature.

A gas having a relative density <1.0 is lighter than air, rises upwards, and therefore a gas with a relative density of> 1.0 is heavier than air and thus drops down natural gas for example, has a specific gravity of 0.55 to 0.75, and liquefied petroleum gas or propane of 1.55.