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Ionic liquids have become the subject of intense research due to their unique chemical properties including negligible vapor pressure and molecular tunability, with a theoretical quantity of 10¹⁸ unique cation/anion combinations. However, a significant proportion of ILs have high melting temperatures (>75°C) which prohibit using these novel salt molecules in processes that operate around room temperature (23°C). Previous studies have shown that the melting point of an ionic liquid can be lowered by absorption of a compressed gas. However, further research is needed to quantitatively characterize the depressed melting point. We will present findings for an ongoing study investigating the melting point depression of the model ionic liquid trimethylsulfonium bis(trifluoromethylsulfonyl)imide [TMSfn][Tf₂N] using compressed carbon dioxide. In this study a gravimetric microbalance with a precision of +/- 1 microgram was used to precisely measure the weight of a [TMSfn][Tf₂N] sample under constant carbon dioxide pressure while temperature was slowly increased. Upon melting the sample weight increased significantly due to sudden carbon dioxide uptake caused by the solubility difference between the solid and liquid phases. The depressed melting point of [TMSfn][Tf₂N] was measured under 5, 10, 15, and 20 bar of carbon dioxide. These methods can be readily applied to other systems and the collected data will provide a quantitative characterization of their phase behavior.