A series of mixed ammonium cobalt-nickel Tutton salts (NH4)(2)[CoxNi1-x](H2O)(6)(SO4)(2) have been doped with a few percent of deuterium. Irradiation of the N-D stretch band I (similar to 2260 cm(-1)) rotates the ammonium group. In the dark this group relaxes back to its original orientational distribution. The HDO molecules also relax, probably by a 180 degrees rotation of a HDO molecule. The samples are at 7 K, and the dark relaxation processes occur by tunneling. The rotation of the ammonium ions must be accompanied by the rotation of the water molecules.