Are the dehydration and hydration of salts reversible

The answer to this question is true, the dehydration and hydration of salts are reversible.

The example for this question would be cobalt(II) chloride salt. This salt has an anhydrous/dry and hydrous/wet form called hexahydrate. The dry form is blue but the wet form is purple. If you put water on the anhydrous form it will become purple. But if you heat it so the water evaporates, the purple hexahydrate will become blue again.

The answer is joseph is observing the colour of the reaction mixture to see whether proteins are present in the given solution.