where 𝜀𝜀 toluene and 𝜀𝜀 THF are the permittivity of toluene and THF, respectively. 𝜙𝜙 toluene and 𝜙𝜙 THF are the weight fractions of toluene and THF in the mixture solutions, respectively. Also, the values of the refractive index of the mixture solutions 𝐶𝐶 mix were calculated by the following equation ,