where ∆χ = χ s -χ w is the difference in the real part molar susceptibilities of the electrolyte and water and ∆φ V = φ V -φ w the difference in their apparent molar volumes. At room temperature, the dielectric constant of water w and its density ρ are approximately 80 and 1000 g/L. This yields χ w ≈ 1.4 so that ρ sol Msol r ≈ 1 1400cm 3 /mol . In cases where the term linear in x in the denominator becomes noticeable, we can use a Taylor expansion of Equ. 18. If the linear term becomes important before the higher order interactions prevail, we would expect an additional contribution in ln γ ± which scales like x × x δ ln(x) = x 1+δ ln(x) which is a member of this family of functions with a different exponent. A similar argument holds for the concentration dependency of R 2 h . In conclusion, in our electrolyte picture the vivid discussion on how much the change in dielectric constant determines the change in ln γ ± is meaningless, since a change in dielectric constant and a higher order expansion are fully equivalent in our description.