The distinct values for T 1 measured in slit pores with identical surface-to-volume ratio suggest differences in the properties of the water near solid Na 2 SO 4 and NaCl surfaces. Density profiles computed along the z-axis normal to the pore surface using MDAnalysis together with the MAICoS Python toolkit show that the maximum density within the first molecular layer is almost twice as large in the case of NaCl as compared to Na 2 SO 4 (Fig. ). The apparent weaker structuring of the water in the case of the Na 2 SO 4 as compared to NaCl could be the consequence of the different atomic roughness of the two solid surfaces: the NaCl block remains perfectly crystalline and its surface along the (100)-plane remains atomically smooth in contact with water (as has been previously observed for example in Refs. ), while the Na 2 SO 4 block is slightly disorganized and its surface is atomically rough in contact with water (Fig. ).