Solubility phenomena in supercritical carbon dioxide (SC-CO2) mixtures have been studied in situ using Raman spectroscopy. A Raman spectroscopy instrumentation has been linked to a high-pressure optical cell. The set-up was tested in the system SC-CO2/alkyl ketene dimer (AKD) under pressures up to 300 bars and temperatures up to 80 degrees C. As a proof of concept, the possibility to study solubility of AKD in SC-CO2 as well as solubility of SC-CO2 in AKD by studying the Raman signal of SC-CO2 has been presented. Statistically tested results show how these competitive phenomena depend on the density region of the SC-CO2. Raman spectra of AKD in the system AKD/SC-CO2 have also been acquired, demonstrating the prospect of quantitative analysis for solubility studies in SC-CO2. Furthermore, this versatile set-up provides information about thermal expansion of the vessel and evidences the need for corrected equations in this commonly used region of pressures and temperatures. (c) 2012 Elsevier B.V. All rights reserved.