Saturation vapor density
||It has been suggested that this article be merged with Saturated fluid, Vapor pressure and Vapor–liquid equilibrium. (Discuss) Proposed since August 2012.|
Saturation vapor density (SVD) is a concept closely tied with saturation vapor pressure. It is useful for getting an exact quantity of water vapor[clarification needed] in the air from a relative humidity (RH).[clarification needed] Given an RH percentage, the density of water in the air is given by RH × SVD = Actual Vapor Density. Alternatively, RH can be found by RH = Actual Vapor Density ∕ SVD. As Relative Humidity is a dimensionless quantity (often expressed in terms of a percentage), vapor density can be stated in units of grams or kilograms per cubic meter.
For low temperatures (below 400 kelvins or so), SVD can be approximated from the SVP by the ideal gas law: P V = n R T where n is the number of moles, which is related by density by n = M ∕ m, where M is the mass of water present and m is the molar mass of water[clarification needed] (18.01528 grams/mole). Thus, setting V to 1 cubic meter, we get P m/ = M/ = density.
R is the gas constant, and T is the temperature in kelvin.