ROLE OF WEIGHTING IN PARAMETER-ESTIMATION FROM SOLID FLUID SUPERCRITICAL EQUILIBRIUM DATA

As an example, the solubility of naphthalene in supercritical CO2 and C2H4 were chosen. Two parameter estimation criteria were compared: use of constant relative error and the maximum likelihood criterion, the latter involves the use of weights derived from the error propagation law. It was found that sigma(DELTAy)2 is very far from being proportio nal to y2, therefore the use of constant relative error is not justifi ed. In the case of the given solid-fluid equilibrium examples, weights based on constant relative error assumption overemphasize the steep p art of the curve where all models fail. None of the models examined we re able to describe C2H4-naphthalene equilibrium. For CO2-naphthalene the BMRK model proved to be better than the other equations of state i nvestigated.