Note on the Pressure Variation of Specific Heats of Gases Derived from Compressibility Data

Values of the rate of variation of cₚ with pressure at constant temperature as calculated from p-v-T data and as determined by direct experiment are compared for oxygen and air over a pressure range of 20 to 100 atmospheres and at 26^∘{} C. The calculated values, while of the same order of magnitude as the experimental, are shown to be very sensitive to small variations in the coefficients of the "equation of state" employed; also to modifications in the method of approximation used in handling such equations. The conclusion is reached that this rate probably diminishes slowly with rising pressure for oxygen in the field considered and that its calculated values cannot at present approach in accuracy what may reasonably be expected from direct calorimetric experiments.