The method of separating a mixture containing common salt, sand and ammonium chloride employs three processes, i.e., sublimation followed by filtration and evaporation. To separate ammonium chloride from the mixture, we should first follow sublimation. In the process, ammonium chloride gets sublimed and a mixture of sand and salt is left behind.
To separate salt from the mixture, we should put the mixture in water. Salt will get dissolved in water and the insoluble sand will be obtained by filtration.
Lastly, salt is separated by evaporating the filtrate, where all the water evaporates leaving behind solid salt.