Explain solid-vapour equilibrium by example.

(N/A) At constant temperature in a closed vessel,the system where a solid sublimes to the vapour phase is known as solid-vapour equilibrium.
$Ex.-1$: If we place solid iodine $(I_2)$ in a closed vessel,after some time the vessel gets filled with violet vapour and the intensity of the colour increases with time. After a certain time,the intensity of the colour becomes constant,and at this stage,equilibrium is attained. Hence,solid iodine sublimes to give iodine vapour,and the iodine vapour condenses to give solid iodine. Properties,colours,etc.,become constant. The equilibrium can be represented as:
$I_{2(s)} \rightleftharpoons I_{2(g)}$ (at constant $T$)
(violet solid) $\rightleftharpoons$ (violet vapour)
Other examples showing this kind of equilibrium are:
$(i)$ $\text{Camphor}_{(s)} \rightleftharpoons \text{Camphor}_{(g)}$ (at constant $T$)
$(ii)$ $NH_4Cl_{(s)} \rightleftharpoons NH_4Cl_{(g)}$ (at constant $T$)