The formation constant, K, of the complex is about 1 but varies with ionic strength.
In these solutions the activity coefficient may actually increase with ionic strength.
Any function of ionic strength will, therefore, be correlated with those phenomena.
We repeat: ionic strength is not a solution property.
For equilibria in solution use a medium of high ionic strength.
The ionic strength also has an effect on reaction rate.
However, the value of K will depend on the ionic strength.
K varies with ionic strength, temperature and pressure (or volume).
The ionic strength can be kept constant by judicious choice of acid and base.
This effect tends to be observed at lower ionic strengths.