Phase behavior data and FTIR spectra along with solubilities and solvatochromic shifts of ionic indicator dyes are reported for binary, ternary and quaternary systems composed of pentaethylene glycol n-octyl ether (C8E5), CO2, water, and n-pentanol as a function of temperature, pressure and composition. With the addition of n-pentanol as a cosurfactant, the water to surfactant ratio, W(o), reaches values as high as 12. As water is added further, a surfactant-rich phase precipitates due to micelle-micelle interactions. Ionic dyes are soluble at levels of 0.03 mM, far in excess of the negligible solubility in pure CO2.