An apparatus has been designed and constructed to measure liquid hydrocarbon solubility in water. Online analysis coupled with gas chromatography has been applied to the determination of binary mixtures of water with benzene and cyclohexane for the temperature range (70 to 150) degreesC. Measurements obtained for benzene show good agreement with literature values and allow us to validate this new method. Increasing the temperature from 70 degreesC to 150 degreesC increases the mole fraction solubility of cyclohexane in water from (19.7 +/- 0.02) x 10(-6) to (131 +/- 3) x 10(-6).