Investigation of SnCl 2 AlCl 3 mixtures by Raman spectroscopy

Raman spectra of the liquid and gas phases are reported for various molten mixtures of SnCl 2 and AlCl 3 . As in other chloroaluminate melts, AlCl 4 − and Al 2 Cl 7 − are the main species present in the liquid phase. However, the spectra indicate the presence of Al 2 Cl 6 ; in addition, the splitting of the ν 3 band and the location of the ν 1 band (341 cm −1 ) observed for AlCl 4 − , are in favour of a strong Sn 2+ ‐AlCl 4 − interaction. A quantitative study of the main ν 1 band ratios in the liquid allows an estimation of the equilibria between the three above‐mentioned species and, consequently, the calculation of the activity of Al 2 Cl 6 . By following the intnsity of the ν 2 Al 2 Cl 6 band in the gas phase, a method for measuring the Al 2 Cl 6 pressure has been developed. Because a phase separation occurs around 87% of Alcl 3 , Raoult's law has been reformulated and the Al 2 Cl 6 activities measured from the liquid and gas phases are in very good agreement. A comparison of the acidity level with other chloroaluminate melts is also made.