Very accurate values of the orthobaric hquid densities are required to provide a basis for the custody transfer of LNG Since it is not possible to measure this property for all mixtures and at all conditions of interest, a reliable and accurate method for the prediction of the densities of LNG mixtures is of great practical impostance to the LNG industry
Very accurate measurements of the orthobaric densities of LNG components and some of the mixtures of interest have recently become avalable [1-4] These measurements have a total uncertainty of less than (01 %) and enable prediction methods to be tested and developed Haynes et al [5] have optimized and tested several methods using the data measured at the NBS Boulder laboratory [1-3] They concluded that the extended corresponding states approach with shape factors ([6,7]) was the most versatile in that it could be applied over the greatest range of pressure, temperature and composition However, the shape factor approach is complex and therefore difficult to use Orthobaric densities are obtained as a result of an iterative calculation to establish vapour-hquid equlbrium The method also requires very accurate values of two binary interaction coefficients These difficulties have led to the appearance of several simple methods where the orthobanc densities [8] or excess volumes [9] are calculated directly
Recently, Miller and Hiza[4] have presented the orthobaric