Editing Solution (chemistry) (section)

=== Gaseous mixtures ===
If the solvent is a [[gas]], only gases (non-condensable) or vapors (condensable) are dissolved under a given set of conditions. An example of a gaseous solution is [[air]] (oxygen and other gases dissolved in nitrogen). Since interactions between gaseous molecules play almost no role, non-condensable gases form rather trivial solutions. In the literature, they are not even classified as solutions, but simply addressed as homogeneous [[mixture]]s of gases. The [[Brownian motion]] and the permanent molecular agitation of gas molecules guarantee the homogeneity of the gaseous systems. Non-condensable gaseous mixtures (e.g., air/CO<sub>2</sub>, or air/xenon) do not spontaneously demix, nor sediment, as distinctly stratified and separate gas layers as a function of their [[relative density]]. [[Diffusion]] forces efficiently counteract [[gravity|gravitation]] forces under normal conditions prevailing on Earth. The case of condensable vapors is different: once the [[saturation vapor pressure]] at a given temperature is reached, vapor excess condenses into the [[liquid state]].