After having assessed the performance of comparing experimental and numerical values of T 1 obtained in bulk systems, we now turn to FFC experiments performed both for NaCl and Na 2 SO 4 salt crusts. In the low frequency regime (ν ≤ 1 MHz), our results reveal a stronger dispersion for T 1 with the frequency ν in the case of Na 2 SO 4 as compared to the NaCl salt crusts (Fig. ). For NaCl, the T 1 spectrum is almost flat for ν ≤ 1 MHz, with T 1 ≈ 1.25 s, i.e., about half of its value in the bulk solution. For Na 2 SO 4 , T 1 has lower values, as compared to NaCl, and reaches value as low as T 1 ≈ 0.15 s for the lowest frequency available. Pore size distributions evaluated from SEM images show that smaller pores are more prevalent in Na 2 SO 4 crusts as compared to NaCl salt crusts (Figs. ). The predominance of smaller pores in the case of the Na 2 SO 4 salt crust could explain, at least in part, the stronger dispersion of T 1 with ν as compared to the NaCl salt crust. However, the smallest pores that can be observed with SEM imaging correspond to a radius of 1 µm, leaving room for further investigation that goes beyond the present paper.