Temperature Drop Effect in Relation to the Determination of the Molecular Heats of Gases

Abstract

IT has been shown in a recent paper¹ by one of us (H.S.G.) that, in the absence of convection, the loss of energy (Q) from an electrically heated wire, compensated for end effects and suitably disposed in a gas, is given by From the above equation, it is evident that measurements of Q and the corresponding pressure (p) over an appropriate range of pressure enable the values of the thermal conductivity (K) of the gas, and also A, to be calculated. Furthermore, it may be shown that if the observations are continued into the low-pressure region where the gas is rarefied, then the heat transfer is governed by the relation If the temperatures T₁ and T₂ are maintained constant throughout the whole range of pressure, then assuming independence of the accommodation coefficient a upon pressure, its value can be deduced directly from equations (1a) and (2), and hence.R, the molecular heat of the gas, can also be determined by substitution in (1a). We have carried out measurements in the case of hydrogen, and the value of at 283° abs. was found to be 2.448 and that of the accommodation coefficient 0.31.