Calorimetric properties of normal heptane from 0-degrees to 520-degrees-k

Abstract

Precise mcasurements of the heat capacity of so lid and liquid n-heptane from 20 0 to 523 0 K arc described. An adiabatic calorimeter, with which were determined also the triple point and the heat of fusion, was used from 20 0 to 370 0 I\:, whereas a drop method was used with a Bunsen icc calorimeter from 273 0 to 523 0 K. These two series of heat-capacity measurements and three other se ries of independent values show a maximum difference of approximately 0.25 percent in the range 50 0 to 370 0 K. Besides the heat capacity, tIl(' enthalpy, entropy, and Gibbs free enerp:y of the solid and liquid at saturation pressures from 0 0 to 520 0 K are derived and tabulated. The same properties of the ideal gas from 298 0 to 470 0 K also arc derived by making use of publishcd precise measurements of gaseous heat capacity, heat of vaporization, and the normal boiling point. Interconsistency in the values of t he various thermal properties is shown by the fact that the vapor pressures calculated from these values ap:rce with those precisely measured by other investigators bet\\"een 200 0 and 372 0 K to \\'ithin 0.1 percent.