Assuming that 𝑧 is a constant for a fixed 𝑓 = 4 and not only for the linear case, 𝑓 = 2, we invert the above computation starting from 𝑧 = 9.1 and convert the viscosity data into experimentally based estimates for the interaction parameter, 𝜒 𝜂 . These estimates are also listed in Table and have a high correlation with the experimental data for 𝜒. The above procedure minimizes errors for individual interaction parameters, but cannot remove all errors on an absolute scale. The main benefit of the above approach is that 𝜒 𝜂 is correct on a relative scale (within the error of the viscosity measurements) such that we can compare experimental data for different solvents with high accuracy.