VAPOR COMPLEXES OF URANIUM PENTACHLORIDE AND URANIUM TETRACHLORIDE WITH ALUMINUM CHLORIDE . NATURE OF GASEOUS URANIUM PENTACHLORIDE

The following three reactions were studied spectrophotometrically: (1) 2UCl4(s) + Cl2(g) = U2Cl10(g), ΔF = 15,132 - 15.38 cal/mol (450-650°K); (2) UCl4(s) + 1/2Al2Cl6(g) + 1/2sCl2(g) = UCl5.AlCl3(g), ΔF = 8914 - 10.74 cal/mol (440- 630°K); (3) UCl4(s) + Al2Cl6(g) = UCl2(AlCl4)2(g), ΔF = 15,780 - 15.30 cal/mol (600-800°K). The volatility ratios Vr = (Pucl in 1 atm ofAl2Cl6)/Puci are found to be ˜107 at 500°K, ˜104 at 600°K, and ˜103 at 700°K. The partial pressure of UCl5.AlCl3 is 34 mm at 500°K, 1 atm of Al2Cl6, and 1 atm of Cl2. Uranium pentachloride was found to vaporize as a dimer molecule. The electronic absorption spectrum of gaseous U2Cl10 was interpreted in terms of two Cl octahedra sharing an edge with U atoms at positions of approximately octahedral symmetry. © 1969, American Chemical Society. All rights reserved.