Volume fraction

In general, the volume fraction or volume fraction is (symbol: υ, φ often ) a component in a mixture, the proportionate volume of the component to the sum of the volumes of all components. It is calculated on the fraction of volume of the component as the numerator and the sum of the volumes of all components of the mixture as the denominator. So For a mixture with m components:

For the common case where only a single component is dissolved in a solvent is present ( m = 2), then:

The volume fraction is therefore one of the possible content information, a measure of the proportional volume of a component to the sum of the volumes. Is the volume fraction of 1 or 100 %, the corresponding component is present in pure form; it is 0, it is not included in the mixture.

In the gas phase, the volume fraction is always identical to the mole fraction (neglecting external forces, such as gravity ), there are distributed here, the molecules of all substances evenly throughout the room.

Multiplying the volume fraction of 100 %, so it can also be in the form of percentage Specify size; this is sometimes still the outdated non DIN-compliant names by volume: - to be found (abbr. vol %). When specifying the composition of gases, or explosive limits specified by this specification is still quite common.

Applications can be found in various fields, particularly chemistry, but also for example in mineralogy and petrology. Here, the volume fraction is used to describe the composition of rocks or minerals ( mixed crystal ), mainly because it is at an optical detection of thin sections comparatively easy to measure the volume of each component.

The application of this content specification in chemistry is usually limited to mixtures in which the substance to be dissolved in liquid ( eg ethanol dissolved in water). The indications of the levels of a substance in a solution as volume fraction is, however, often avoided because the total volume of the solution can be fundamentally different from the sum of the individual volumes (see volume contraction and volume dilatation ). Instead expediently used the volume concentration. For the same reason, the use of the volume fraction for porous and bulk materials is not suitable. Much better and without difficulty in defining will determine the mass fraction; this value has the additional advantage of not being dependent on the temperature.