Le Système Gazeux Gallium–Chlore: Etude par Spectrométrie Raman. 2–Analyse Quantitative

Abstract

Abstract Procedures for the quantitative treatment of Raman spectra are proposed for the investigation of gallium–chlorine gaseous mixtures. They are based on correlations between pressures and Raman band intensities and require a knowledge of reliable entropy and heat capacity data for the main gaseous species. For the ratio Cl/Ga=3 and between 590 and 690 K, the pressure determinations from the band intensity evolution corresponding to the symmetric vibrational modes ‘ν 1 ’ of Ga 2 Cl 6 and GaCl 3 confirm the starting consideration of the single equilibrium Ga 2 Cl 6 (g)⇌2GaCl 3 (g). They lead to an enthalpy of dissociation of Ga 2 Cl 6 very close to the literature data. For Cl/Ga3 and between 800 and 950 K, the treatment of the Raman spectra is performed by computation of the GaCl spectrum in order to discriminate between the GaCl 3 ‘ν 1 ’ band intensity and the GaCl ‘ν s ’ branch intensity. This intensity difference and the GaCl ‘ν Q ’ branch intensity are used for pressure determinations. The results are consistent with the proposed equilibrium 2Ga(l)+GaCl 3 (g)⇌3GaCl(g). They lead to a calculated reaction enthalpy that allow one to select a reliable value for the enthalpy of formation of GaCl.