Phase V−T diagrams of solid hydrocarbons. part III: Cyclic compounds.

This article focuses on the construction and analysis of pressure–temperature (P−T) and volume–temperature (V−T) phase diagrams for several cyclic hydrocarbons, including benzene (C₆H₆), cyclopentane (C₅H₁₀), thiophene (C₄H₄S), tetrahydrofuran (C₄H₈O), cyclohexane (C₆H₁₂), furan (C₄H₄O), and the less-studied cyclohexene (C₆H₁₀). Using both literature data and new experimental results from isochoric thermal conductivity studies, the authors determined molar volume changes during melting, phase boundaries of high-temperature phases, and thermal pressure magnitudes. Experimental derivatives of melting pressure with respect to temperature (dPₘ/dT) were compared with values calculated via the Clapeyron-Clausius equation, showing good agreement. Thermal pressure values (dP/dT)_V ranged from 0.8 to 3.6 MPa/K across the compounds, correlating with melting line slopes, with an average ratio of (dPₘ/dT)/(dP/dT)_V around 2.5 except for benzene, where it is 1.5.