We examined the impact of various factors on the salt effect, which enhances the solubility of difficultly soluble salt, exerted by the presence of inert electrolyte that has neither common cation nor anion. It was conducted experimentally, by examining the ratios of solubility products of different salts in different solvents, as well as at different ionic strength. The goal was to select such ionic strength where the activity coefficient is minimal, that is, the enhancing effect is maximal. It was established that such factors as dielectric permittivity of the solvent, the anion charge affect enhancing coefficients but do not affect the value of ionic strength at which the salt effect is maximal. It was found that dielectric permittivity of the solvent has a direct impact on the multiplying factor of the “salt effect”; we also established dependence of the anion charge and the magnitude of the “salt effect”. In addition, it was influenced by the degree of bond ionicity between the cation and the anion, in other words, the difference in electronegativities according to Pauling (EN). The obtained data are of high theoretical interest for physical chemistry, as well as for the design of new adsorbents and in other situations where it is required to improve the solubility of a difficultly soluble salt.