Correction to the Furry–Jones–Onsager Theory of the Thermal-Diffusion Column

Abstract

The famous theory of the thermal diffusion column derived by Furry, Jones, and Onsager is based on the implicit premise that the mass of a component in a binary mixture is given by the product between the mass of the whole mixture and the molar concentration of that component. The premise is strictly correct only if m ₂/m ₁=1, where m ₁ and m ₂ are the molecular masses of the two components. Here a corrected theory is derived, which is valid for any value of the ratio m ₂/m ₁. Comparison of the original and corrected theory shows that for the case of a column operated at total reflux, the two theories give identical results. However, for productive operations the original Furry–Jones–Onsager theory can produce deviated data. The magnitude of the deviation depends on the ratio m ₂/m ₁. It is: a) null for m ₂/m ₁=1, b) small for heavy isotopes (up to 0.86% for a ²³⁵UF₆–²³⁸UF₆ mixture), c) significant for light isotopes (up to 33% for a ³He–⁴He mixture), and d) very high for m ₂/m ₁≫1 (absurd results are obtained for m ₂/m ₁=10).

Keywords:

• Thermal-diffusion column
• Isotope separation
• Helium 3

Acknowledgments