Some Physical Properties of Compressed Gases. I. Nitrogen

Abstract

The writers have adjusted and extrapolated the compressibility data obtained by Bartlett and his collaborators on nitrogen, so that very accurate $p-v-T$ data from — 70 to 600° and up to 1200 atm. are available. A suitable graphical scheme has been devised for obtaining the derivatives ${\left(\frac{\mathrm{dv}}{\mathrm{dp}}\right)}_T$, ${\left(\frac{\mathrm{dv}}{\mathrm{dT}}\right)}_p$, ${\left(\frac{d^{2}v}{d{T}^2}\right)}_p$ at any point in order that some of the physical properties of the gas can be calculated. This graphical scheme depends on the relation of $\alpha \equiv \frac{\mathrm{RT}}{p-v}$ and $\Delta \equiv v(\frac{\mathrm{pv}}{\mathrm{RT}}-1)$ to $p$, $v$, $T$, and on the relations of the derivatives of $\alpha$ and $\Delta$ to the derivatives of $v$. Errors in the estimation of the slope of an $\alpha$ or $\Delta$ curve at any point introduce much smaller errors into the derivatives of $v$, since the derivatives of $\alpha$ and $\Delta$ enter as correction terms to the derivatives of $v$ just as $\alpha$ and $\Delta$ are corrections to $v$ itself.