Uranium(III) chloride.

dark purple crystal(s); somewhat hygroscopic; obtained by reacting UH3 with HCl at 250°C–300°C; used in molten salt electrolytes to refine uranium metal [KIR83] [MER06]

Completely pure UCl4 is reduced with H2 in the same tube in which it is prepared. The reduction proceeds below red heat and then at dull-red heat, until the off-gases are free of HCl. Absolutely pure H2 must be used. The dull-brown, very hygroscopic UCl3 adheres strongly to glass. Thus, when the mechanically separated product is dissolved, some brown to brick-red U (IV) silicate is always obtained as a residue.