Densities of the solutions of gallium, yttrium, lanthanum, gadolinium, and lutetium trifluoromethanesulfonates in methanol have been determined at temperatures ranging from (283.15 to 313.15) K. The sound velocities in these systems have been measured at T = 298.15 K. From obtained data the standard partial molar volumes and their temperature derivatives as well as standard partial molar adiabatic compressibilities for ions in solutions have been estimated. The results have been discussed on the basis of the classical model of ion in solution and compared with our earlier findings for divalent cations. The importance of the numbers of solvent molecules in first salvation spheres of ions has been revealed. (C) 2011 Elsevier Ltd. All rights reserved.