The second moment and spin lattice relaxation times have been obtained forcis-diaquotetramminecobalt(III)sulfate between 77 and 310 °K. The results suggest that one of the ammine ligands is unique, reorienting more slowly at a given temperature than the others. Both water ligands undergoC2- jumps. Although whole ion rotation does not occur libration does, and the second moment is interpreted in terms of such a torsional motion.