Copper II sulfate CuSO4 decomposes before reaching its boiling point. It undergoes a series of transformations when heated. At around 110C, it loses water molecules and converts to its pentahydrate form CuSO45H2O . As the temperature increases, it continues to lose water molecules and eventually turns into an anhydrous form CuSO4 at around 650C. At temperatures above 650C, CuSO4 starts to decompose into copper II oxide CuO and sulfur trioxide SO3 . Therefore, it does not have a specific boiling point at 1 atmosphere.