SUBLIMATION

SUBLIMATION

Sublimation is the process of vaporizing a solid substance and
condensing the vapors to again form the solid directly, without
passing through an intermediate liquid state. There are very few substances which vaporize without melting, but in all cases of sublimation, the change from the vapor to the solid state, is direct, and without any formation of liquid. The sublimed body is recovered unchanged chemically, but its physical properties are often more or less altered.
Sublimation is influenced by the pressure within the vessel, and
is generally carried on under atmospheric pressure only. The
process is employed as a means of purification of certain substances, which are heated in closed pans or retorts. In most. eases, the temperature does not exceed a low red heat. Dissociation often occurs in the process.