Sublimation of Iodine at Various Pressures.

The aim of this article is to elucidate some interesting phenomena, which can be observed in the process of heating solid iodine in closed vessels at various pressures. The experiments provide useful possibilities for discussing the following items: vaporization and melting of iodine crystals at atmospheric pressure; long storage of iodine crystals in air and in vacuum; temperature at which iodine vapors above crystals in a closed vessel becomes visible; the rate of iodine sublimation in high vacuum; “jumping” of heated iodine crystal in vacuum and “jet force” which emerges at different temperatures; diffusion of iodine vapors and “random walk” of iodine molecules; experimental determination of mean free path and collision frequency; mean free path in real life; calculation of the number of iodine atoms in equilibrium with molecular iodine at boiling point; and safety considerations (strength of glass ampules of different diameters against internal and external pressure). The article and questions therein...