The phase behavior of solutes in SCF is an important aspect, which is often overlooked in the solubility determinations. Solid solutes when in contact with supercritical CO2 can exhibit complex phase behavior such as depression in melting point resulting in multiple phases, and therefore can considerably influence the determination of solid solubility. The purpose of this study is to research solubilities of aromatic carboxylic acids and substituted phenols in SCF- CO2 using the SFT phase monitor.