Inversion Temperature in the Separation of Isobaric C O Molecu les by Thermal Diffusion

In specially constructed thermal diffusion columns separations between the isotopic mixtures 1 2 C 1 8 0/ 1 2 C 1 6 0 and 1 4 C 1 6 0/ 1 2 C 1 6 0 were measured at average temperatures ranging from T = 260 ° K to T = 465 °K . At temperatures above 320 ° K 1 4C 1 60 concentrates more strongly in the cold region than 1 2 C , 8 0 . Below this temperature the opposite effect is taking place: the thermal diffusion factor a ( 1 2 C 1 8 0 / 1 2 C 1 6 0) is greater than a ' ( 1 4 C 1 6 0 / 1 2 C 1 6 0) . All separations were carried out at temperatures for which the heavier molecule concentrates in the cold region.