The adiabatic compressibility, beta, of the immiscible liquid mixture (LiF + CsCl) along the saturation line was experimentally investigated in the temperature range from the melting point to the critical mixing temperature using sound velocity values, u, measured by the pulse method, and density quantities, rho, determined using the hydrostatic weight procedure based on the relationship beta = u(-2)rho(-1). The coefficients of the temperature dependencies for the compressibility, sound velocity and density of the upper and lower equilibrium phases have opposite signs because of the superposition of the thermal motion intensity of the ions and the change in the phase compositions. The differences Delta beta, Delta u and Delta rho for the equilibrium phases decrease with temperature elevation. The temperature dependencies of the compressibility, sound velocity and density difference are described using the empirical equations Delta beta approximate to (T-c - T)(1.004), Delta u approximate to (T-c - T)(1.003) and Delta rho approximate to (T-c - T)(0.504). (C) 2019 Elsevier Ltd.