Shape of the Coexistence Curve in the Perfluoromethylcyclohexane-Carbon Tetrachloride System

Transition temperatures for the transition from the one-phase to the two-phase condition have been observed for the perfluoromethylcyclohexane-carbon tetrachloride system. It is found that (Tc—T+0.001°)⅓ (where Tc, which is equal to 28.623°, is the observed critical temperature) is a linear function of the molecular fraction of carbon tetrachloride. As is indicated by the form of this function there appears to be a flat horizontal portion at the top of the coexistence curve, which extends from 0.5375 to 0.5625 volume fraction CCl4. It involves such a small temperature range as to be almost unobservable and the flat top is much less marked than in the cyclohexane-aniline system. The melting point of perfluoromethylcyclohexane has been found to be —41.72°C.