Density, Viscosity and Surface Tension of Molten Aluminum Chloride

Density, viscosity and surface tension of molten aluminum chloride have been measured precisely to understand its unique physicochemical properties by using a float method, a capillary viscometry and a capillary rise method, respectively. The apparatuses used are all made of quartz or Pyrex glass and the melt was sealed in them completely. Density, viscosity and surface tension obtained are considerably lower than those of other conventional molten salts. The temperature corresponding to critical temperature could be estimated from the surface tension. The hypothetical melting temperature by assuming that the molecular solid which consists of Al₂Cl₆ was estimated to be almost 1.50 K lower than melting temperature of real ionic crystal of aluminum chloride. These results suggest that the molten aluminum chloride is different in the condition of the study from other typical molten salts, namely it is considerably superheated liquid due to the structural change on melting from ionic crystal to molecular liquid. The lower values measured in this work are attributed to such a superheated state.