The Somayajulu correlation for the surface tension revisited

The Somayajulu correlation for the surface tension was proposed in 1988. It is a three-parameter generalised equation with certain theoretical basis, which is valid for temperatures from the triple point to the critical point. According to its author, this equation not only fits the data well but also is good for interpolation between the normal boiling point and the critical point. As the data used in the original paper where published earlier than 1975, it seems to be adequate to revise the validity and accuracy of the correlation by adding more recent experimental values. For that, we use here mainly the data included in the DIPPR and DETHERM databases for the 64 fluids considered in the original Somayajulu paper. Some data in the mentioned databases were not considered when a clear disagreement between them was found. Moreover, for some particular fluids other available sources of data were added. We found a good general agreement between the Somayajulu correlation predictions and the data for 45 fluids. Moreover, for another 15 fluids the model can be improved, so that new values for the parameters are given here. Finally, we found that for another four fluids: hydrogen telluride, krypton, neon, and nitrosyl fluoride, the published parameters lead to values in clear disagreement with the available data. New parameters are also given for them. In conclusion, the Somayajulu correlation is an accurate model when the appropriate parameters are considered.

► The validity and accuracy of the Somayajulu correlation for the surface tension is checked.
► Data from DIPPR, DETHERM, and other sources for 64 fluids are checked.
► The original Somayajulu correlation is clearly inadequate for four fluids: hydrogen telluride, krypton, neon, and nitrosyl fluoride.
► New coefficients for the Somayajulu correlation are given for 19 fluids.