liquid; etches glass slowly at room temp; appreciable vapor pressure at room temp; enthalpy of vaporization 44.52 kJ/mol; enthalpy of fusion 49.96 kJ/mol [CRC10] [MER06]
A small nickel or platinum boat containing VF 4 is placed in a
nickel tube and gradually heated to 650°C in a stream of dry N2
.
The exit gases are collected in a large-diameter quartz trap maintained at —78°C. The trap is attached to a drying tube with anhydrous KF to exclude atmospheric moisture. The heating process
must be effected slowly, since otherwise the unreacted VF4 is
blown out of the reaction tube. The product is allowed to cool in
a nitrogen stream and the VF5 is discharged directly from the
gas trap into a storage container. A greenish-yellowish residue (VF4) remains in the boat. The yield is almost quantitative.
The product is stored in sealed iron, nickel, copper or platinum containers.
