Anhydrous calcium chloride is used after washing your organic product with water. the purpose of this step is to:

The purpose of washing the organic product that contains water with anhydrous calcium chloride is to remove water from the organic product, thereby, increasing its purity. Calcium chloride is known to be one of the most effective drying agents together with sodium sulfate and magnesium sulfate. It is especially used for hydrocarbons. It is an inorganic salt that readily takes up the water from the organic product. 

Anhydrous solids are the crystallized crystals when the hydrate form of the compound undergoes crystallization. Hence, when an anhydrous salt is placed in an aqueous environment, it will absorb water in order to be a hydrate once again. Thus, anhydrous calcium chloride is used to absorb the water to separate it from the organic product.

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