Editing Equilibrium constant (section)

==== Competition method ====
A particular use of a stepwise constant is in the determination of stability constant values outside the normal range for a given method. For example, [[EDTA]] complexes of many metals are outside the range for the potentiometric method. The stability constants for those complexes were determined by competition with a weaker ligand.
:ML + L′ {{eqm}} ML′ + L {{spaces|5}} <math>[\mathrm{ML}']=K\frac{[\mathrm{ML}][\mathrm{L}']}{[\mathrm{L}]} = K \frac{\beta_\mathrm{ML}[\mathrm{M}][\mathrm{L}][\mathrm{L}']}{[\mathrm{L}]}= K \beta_\mathrm{ML}[\mathrm{M}][\mathrm{L}']; \quad \beta_{\mathrm{ML}'}=K\beta_\mathrm{ML}</math>
The formation constant of [[Palladium(II) cyanide|[Pd(CN)<sub>4</sub>]<sup>2−</sup>]] was determined by the competition method.