text: Henrys law has been shown to apply to a wide range of solutes in the limit of infinite dilution (x' → 0), including non-volatile substances such as sucrose. In these cases, it is necessary to state the law in terms of chemical potentials. For a solute in an ideal dilute solution, the chemical potential depends only on the concentration. For non-ideal solutions, the activity coefficients of the components must be taken into account:
  where  for a volatile solute; c° = 1 mol/L.
  For non-ideal solutions, the infinite dilution activity coefficient γ depends on the concentration and must be determined at the concentration of interest. The activity coefficient can also be obtained for non-volatile solutes, where the vapor pressure of the pure substance is negligible, by using the Gibbs-Duhem relation:
  By measuring the change in vapor pressure (and hence chemical potential) of the solvent, the chemical potential of the solute can be deduced.
  The standard state for a dilute solution is also defined in terms of infinite-dilution behavior. Although the standard concentration c° is taken to be 1 mol/L by convention, the standard state is a hypothetical solution of 1 mol/L in which the solute has its limiting infinite-dilution properties. This has the effect that all non-ideal behavior is described by the activity coefficient: the activity coefficient at 1 mol/L is not necessarily unity (and is frequently quite different from unity).
  All the relations above can also be expressed in terms of molalities b rather than concentrations, e.g.:
  where  for a volatile solute; b° = 1 mol/kg.
  The standard chemical potential μ°, the activity coefficient γ and the Henrys law constant H' all have different numerical values when molalities are used in place of concentrations.