The thermomagnetic torque in selected polar gases

Abstract

The purpose of this investigation was to study the thermomagnetic torque (TMT) characteristics of selected polar gases. The polar gases studied were nitrous oxide (N₂O), carbonyl sulfide (OCS), hydrogen chloride (HCl), deuterium chloride (DCl), and trifluromethane (CHF₃) at 310 K. The shape of the curve the TMT times the gas pressure divided by the temperature difference τP/ΔT versus the magnetic field divided by the pressure H/P and, by extrapolation from the data, the parameters τP/ΔT and H/P at the curve maximum in the absence of Knudsen effects (τP/ΔT)[superscript infinity, subscript m] and (H/P)[superscript infinity, subscript m] were determined. The shape of τP/ΔT versus H/P was θ/1+θ² + 2θ/1+4θ² where θ is proportional H/P for each gas to within the experimental uncertainty. The parameters (τP/ΔT)[superscript infinity, subscript m], in units of 10�� dyn cm torr/K, and (H/P)[superscript infinity, subscript m], in units of k0e/torr, are: for N₂O, -39.2 ± 2.2 and 14.4 ± 0.73; for OCS, -21.2 ± 0.4 and 4.51 ± 0.26; for HCl, +3.4 ± 1.4 and 5.25 ± 0.46; for DCl, +5.0 ± 2.5 and 8.53 ± 0.24; and for CHF₃, -2.92 ± 0.17 and 46.4 ± 2.4. For the gases HCl and DCl, (H/P)[subscript m] decreased as P was decreased. This change is opposite from what is found in the diamagnetic gases and the other polar gases. Using the theory of Levi, et al., including surface effects, theoretical calculations of (τP/ΔT)[superscript infinity, subscript m] and (H/P)[superscript infinity, subscript m] were made and were compared to the measured values. For HCl, the theoretical values of (τP/ΔT)[superscript infinity, subscript m] and (H/P)[superscript infinity, subscript m] were 0.596 x 10�� dyn cm torr/K and 6.58 k0e/torr. For DCl, they were 0.885 x 10�� dyn cm torr/K and 4.51 k0e/torr. The calculated values of (τP/ΔT)[superscript infinity, subscript m] and (H/P)[superscript infinity, subscript m] for HCl and DCl are outside of the experimental uncertainties of the measured values.