Abstract: A method and apparatus for studying the conditions under which multiple condensed phases form during production, transportation, and processing of crude oil and other organic liquids. The sample temperature and pressure are controlled, and changes in fluorescence and/or electrical conductance or conductivity occurring within the sample due to formation of multiple condensed phases are detected. The measurements are made using a cell containing the liquid sample at elevated temperature and pressure. The cell has a generally cylindrical housing and separate means for visually inspecting a liquid sample which is present within the cell, controlling the temperature of the liquid sample, controlling the pressure of the liquid sample, detecting fluorescence changes occurring within the sample, and determining the electrical conductivity of the sample.