Surface tension and cohesive energy density of molten salts

The surface tensions sigma of a large number of molten salts are known as (decreasing) linear functions of the temperature. They may be compared at a so-called "corresponding temperature", of which 1.1T(m) is a good choice (T-m/K is the melting temperature). It is shown that for highly ionic molten salts of the 1:1, 1:2, and 2:1 charge types sigma is a linear function of the cohesive energy density, ced. Molten salts with pronounced partial covalent bonding have generally much smaller surface tension values than highly ionic ones having similar values of the ced. The correlation between sigma and ced is rationalized and compared with correlations in the literature, but the latter pertain only to the alkali metal halides. (C) 2013 Elsevier B.V. All rights reserved.