Evaporation and decomposition of eutectics of cupric chloride and sodium chloride

Abstract

The kinetics and mechanisms involved in evaporation and decomposition of CuCl₂(s) from the eutectics of CuCl₂(s)–NaCl(s) were investigated in this work. Based on DTA/TG, it was found that anhydrous CuCl₂(s) was decomposed into CuCl(s) at 455.5 °C; then, the CuCl(s) thus obtained melt at the same temperature. After that small part of the CuCl(l) evaporated at 488.5 °C and most of CuCl(l) aggregated to form Cu₃Cl₃(l) in the temperature range of 488.5–667.3 °C. The boiling point of Cu₃Cl₃(l) was 667.3 °C. CuCl₂(s) was completely decomposed into CuCl(s) in 20–40 min at 500–650 °C in Ar atmosphere. The evaporation rate constants (k) of CuCl₂(s) in the time range of 20–120 min were 0.0018, 0.0072 and 0.0158 mg min⁻¹ at the temperatures of 500, 600 and 650 °C, respectively, which were very close to the corresponding values of CuCl(s). Anhydrous CuCl₂(s) reacted with NaCl to form some eutectics with a eutectic point of 374 °C. The k values of the eutectics were about one-tenth and half of those of pure CuCl₂ at 600 and 500 °C, respectively. The evaporation of eutectic was inhibited more at a higher temperature of 600 °C. The addition of NaCl significantly inhibited both evaporation and decomposition of CuCl₂(s) from the eutectics.