Preferential Solvation of bis-(2,2′-bipyridyl) biscyanoiron(II) was investigated in 2-ethoxy ethanol water binary aqueous mixtures. The treatment showed that preferential solvation by 2-ethoxy ethanol occurs. The preferential solvation constant at 298.15° K was found to be equal to (4.96 ± 0.06) and the free energy of preferential solvations ΔG has a value of 3.97° KJ mol−1