Mixture:

Most of the matter in our surroundings exists as mixtures of two or more components. Examples: milk, soil, sea water, etc. A mixture shows the properties of its constituent elements. The components of a mixture can be separated by physical methods like handpicking, filtration and so on. Sometimes special techniques have to be used for the separation of the components of a mixture.

Separation of components from a mixture of sand, ammonium chloride and salt:

Sublimation:

Sublimation is the process of transition of a substance from the solid to the gaseous state without passing through the liquid state. To separate mixtures that contain a sublimate with volatile component from a non-sublimate impurity, the sublimation process is used. Ammonium chloride changes directly from solid to gaseous state on heating. The gaseous form of ammonium chloride can be cooled easily to get a pure solid. Other examples of solids which sublime are camphor, naphthalene, anthracene, iodine, etc. 

The remaining components of the mixture are salt and sand. Salt is soluble in water and sand is a non-water soluble substance that can be separated by the process of filtration. The insoluble sand remains in the filter paper while the filtrate contains the dissolved salt. 

Evaporation Technique:

Evaporation technique is used to separate salt from the filtrate. Common salt does not decompose during evaporation. As the water evaporates, fewer and fewer water molecules are present to keep the salt particles apart. The salt therefore recrystallizes and can be collected.