Densities (r) and refractive indices (nD) of potassium hexacyanoferrate(II) trihydrate of different molal concentrations (m=0.010-0.102 mol·kg-1) in aqueous 0.1 M HCl solutions were measured at 35 0C. Specific refractions (RD) were calculated from refractive index and density of solutions. Apparent molar volumes ( j v) were calculated from density data and partial molar volumes were evaluated by Masson’s relation. Physicochemical behavior of experimental solutions has been studied in terms of ion-ion and ion-solvent interactions.