High pressure solid–solid and solid–liquid transition data for long chain alkanes

The thermal behavior, upon heating, was studied for four alkanes: eicosane, tetracosane, triacontane, and tetracontane at pressures from (10 to 150) MPa. Using a transitiometer, the calorimetric signal, pressure, and temperature were measured at a very slow heating rate to guarantee thermal equilibrium.It was found that from the compounds studied, eicosane was the only one that did not present a solid–solid transition; the other compounds show a solid–solid transition a few Kelvin below the solid–liquid transition temperature. This solid–solid transition disappears when the pressure is increased in a triple point of type: solid + solid + liquid.