Thermal Diffusion with Boron Trifluoride

With B${\mathrm{F}}_3$ gas at atmospheric pressure in 7 meters of hot wire Clusius and Dickel columns, with $\Delta T=400\mathrm{}$°C, the equilibrium separation factor for ${\mathrm{B}}^{10}$ ${\mathrm{F}}_3$/${\mathrm{B}}^{11}$ ${\mathrm{F}}_3$ was 1.32±0.12, reached in slightly over three days. Our best separation factor per meter of column indicates a thermal diffusion constant $\alpha \cong +5.0\mathrm{}\times {10}^{-4\mathrm{}}$ and $R_T\cong 0.06$. Experience in purifying commercial B${\mathrm{F}}_3$ gas and with mass spectrometer analyses is discussed.