The far infrared spectra of some solid and molten alkali metal nitrates and sodium nitrite have been measured at various temperatures. The dipole moment correlation functions obtained from these spectra by Fourier transformation are presented and are connected with a solid state formalism. These dipole correlation functions give a measure of the lifetime of the correlated motions in the liquid phase. The lifetimes for the molten salts are of the order of 10-1 2-10-13 sec. High anharmonicity and large fluctuations characterize the liquid phase.