Describe an experiment for the preparation of pure ammonium chloride from a mixture of common salt and ammonium chloride

Ammonium chloride can be obtained from the mixture of sodium chloride using sublimation method. Place the mixture in a heat proof vessel (glass bottle / test tube or similar) .Continue heating the mixture gently, the ammonium chloride will sublime (change from solid to gas without ever being liquid) leaving the sodium chloride behind. The ammonium chloride will condense on the top of the bottle / test tube. From there it can be collected as pure ammonium chloride compound.