The authors have investigated the variation of the dielectric constant, the density and the refractive index of dilute solutions of Al₂Br₆ in CS₂ + C₆H₆, with molecular ratios 0,0533, 0,1029 and 0,1773 mole C₆H₆/mole CS₂. It has been found that dielectric constant and caculated total polarisation P₁₂ do not vary linearly as a function of the ratio X = moles AI₂Br₆/moles C₆H₆; the diagrams show caracteristic deviations (maxima, minima and "steps"), which may be interpreted by the formation of several polar compounds between C₆H₆ and Al₂Br₆. This conclusion is supported by a previous study of the nuclear magnetic resonance of the same solutions.