On the influence of ionic strength on the equilibrium constant of copper-murexide interaction

The concentration formation constant for the 1:1 complex between copper(II) and murexide in aqueous solutions has been measured as a function of ionic strength by spectrophotometry at 25 degrees . There is an inverse relationship between the K(c) values and ionic strength. The formation constant at infinite dilution was found to be 6.16 x 10(4). The distance of closest approach for the Cu(2+) ion was estimated as 4.3 +/- 0.3 A.