15513-94-7

Brown-black, crystalline powder. Very hygroscopic. Readily soluble in water giving a brown solution which turns gradually green in air. Also soluble in absolute ethanol; insoluble in benzene, CCl4, CS2. d4.2.

Formed when metallic V and I₂ are heated at 300°C under the vapor pressure generated by the latter.
V + 3/2I₂ = VI₃
Vanadium metal (turnings or powder) and excess I₂ are placed in a hard glass or fused quartz tube, closed at one end; the tube contents are cooled to — 80° C; the tube is thoroughly evacuated and then melt-sealed to a short total length. A vigorous reaction sets in on heating. The entire tube is heated for a while at temperatures up to 300°C in order to achieve product uniformity. The excess I2 is then allowed to distill off into a somewhat cooler zone, and the tube is quickly cooled and opened.