What are the triple point pressure and temperature for pure cyclohexane?
The NIST REFPROP (Reference Fluid Thermodynamic and Transport Properties) program reports the triple-point temperature of cyclohexane as 279.47 K.
The program refers to: S. G. Penoncello, R. T. Jacobsen, and A. R. H. Goodwin: “A Thermodynamic Property Formulation for Cyclohexane”, International Journal of Thermophysics, Vol. 16., No. 2, 1995, 515–531.
This publication mentions the triple-point temperature as T = 279.47 K and the triple-point pressure as p = 5.388 kPa.
The given reference is: J. G. Aston, G. J. Szasz, and H. L. Fink, J. Am. Chem. Soc. 65  1135 (1943).



The following p-T diagram (made using REFPROP) shows the melting line (solid-liquid equilibrium, blue) and the vaporization line (liquid-gas equilibrium, red), which meet at the solid-liquid-gas triple point. Unfortunately, REFPROP does not include the sublimation line for cyclohexane.