Abstract−Equations of state play an important role in chemical engineering designs, and they have assumed an expanding role in the study of the phase equilibria of fluids and fluid mixtures. In this report, a modified Peng-Robinson equation of state by Danesh et al., a modified Peng-Robinson equation of state by Gasem et al., and the Mansoori-Mohsen Nia-Modarress equation of state are used to predict the solubility of some solids in supercritical carbon dioxide. The systems studied were binary mixtures containing supercritical carbon dioxide with Ascorbic acid, Ascorbyl palmitate, Butyl hydroxyl anisole, Dodecyl gallate and Propyl gallate. Interaction parameters for the studied systems are obtained and the percentage of average absolute relative deviation (%AARD) in each calculation is displayed. Key words: Equation of State, Solid Solubility, Supercritical Carbon Dioxide INTRODUCTION The need to understand the fundamentals of supercritical fluid processing and the application of this technique to an increasingly wide range of materials and conditions continues to grow. Carbon dioxide as a supercritical fluid has many excellent properties such as non-toxicity, non-explosiveness, ready availability and ease of removal from the extracted products. In the last few decades, the solubilities of different solutes in supercritical fluids have been measured extensively [Choi et al., 1996, 1997; Chang et al., 1996; Noh et al., 1995; Hong et al., 1990]. Since solubility data of solids and their mixtures in supercritical fluid are limited and the accurate measurement of the solid solubility in supercritical fluid is also difficult and time consuming, there is thus considerable interest in mathematical models that can accurately predict the phase behavior of such systems. Equations of state in combination with mixing rules are currently the most widely models used for the calculation of solubility of components in supercritical fluids [Skerget et al., 2002]. Some of the works done in this area are [Neau et al., 2005; Lee et al., 2005; Yener et al., 2005]. In this study a modified Peng-Robinson equation of state by [Danesh et al., 1995] (MPR1), a modified Peng-Robinson equation of state by [Gasem et al., 2001] (MPR2) and The Mansoori- Mohsen-Nia-Modarress equation of state [Mansoori et al., 2003] (MMM) are used to predict the solubility of Ascorbic acid, Ascorbyl palmitate, Butyl hydroxyl anisole, Dodecyl gallate and Propyl gallate. Interaction parameters for the studied systems are obtained and the percentage of average absolute relative deviation (%AARD) in each calculation is displayed.

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