Abstract
An apparatus has been constructed and described for investigating the effusion of gases through a small orifice, and the method has been applied to helium between the temperatures of 1000\ifmmode^\circ\else\textdegree\fi{} and 2000\ifmmode^\circ\else\textdegree\fi{}K, and at pressures from 0.2 to 0.8 mm of mercury. The kinetic theory applying to the problem is discussed. It has been found that the effusion of the monatomic gas helium follows Knudsen's expression $N=\frac{\mathrm{PA}{N}_{L}}{{(2\ensuremath{\pi}mkT)}^{\frac{1}{2}}}$ Keeping the rate of flow constant, i.e., $N={N}_{0}$, $P={P}_{0}{(\frac{T}{{T}_{0}})}^{\frac{1}{2}}$ if allowance is made for viscosity and slippage effects of the gas in the orifice chamber. It is suggested that the apparatus may be used to measure high temperatures as a gas thermometer. Experiments were carried out with hydrogen at temperatures from 1000\ifmmode^\circ\else\textdegree\fi{} to 1900\ifmmode^\circ\else\textdegree\fi{}K, but an interpretation of the results is not possible because of the presence of both molecular and atomic hydrogen in the orifice chamber at these temperatures.
Published Version
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