Sublimation of phthalic anhydride

A 10x speed video showing the sublimation of phthalic anhydride, forming the characteristic woolly crystals.
The heating was carried out using an induction heater using the ZVS driver and a flat, uncooled work coil, at around 50W.

The phthalic anhydride is placed in a nickel crucible inside a Pyrex dish, the crystals collecting inside the dish.

The same apparatus and procedure was used for the preparation of phthalic anhydride from phthalic acid, however the re-sublimation of the anhydride is shown here, rather than the thermal dehydration of phthalic acid, as this produces water vapour which obscures the view inside the dish.