Thermal conductivity and heat capacity of cyclohexane under pressure

The transient hot-wire technique was used to determine the thermal conductivity, λ, and the specific heat capacity per unit volume, pc_p, of cyclohexane up to 1.5 GPa in the range 120–340 K. The measurements were carried out in a piston-cylinder apparatus, 45 mm in internal diameter, cooled by liquid nitrogen. There is only a small (6%) increase in λ on freezing, while there is an increase by a factor of two corresponding to the plastic→ normal crystal transition. The variation of λ with temperature (T) at P = 0.03 GPa is $\text{d(lnλ)}\text{dT}\text{= ?2.2×10}{}^{\mathrm{?3}}\text{K}{}^{\mathrm{?1}}$ for the liquid and $\text{d(ln λ)}\text{dT}\text{= ?0.9× 10}{}^{\mathrm{?3}}\text{K}{}^{\mathrm{?1}}$ for the plastic crystalline phase. In the norm crystal phase an approximate T^?1 dependence is observed. Within each of the phases λ increases linearly with pressure, and the slope of λ (P) is smallest in the plastic crystal phase. The existence of a recently reported new high pressure phase is evident from conductivity data. Qualitative ρC_p -results are reported.