What is the percentage of water crystalline in blue vitriol?

Blue vitriol, or copper(II) sulfate pentahydrate (CuSO₄·5H₂O), contains five water molecules for each formula unit of copper(II) sulfate. The molar mass of anhydrous CuSO₄ is approximately 159.61 g/mol, and the molar mass of the five water molecules is about 90.08 g/mol. Therefore, the percentage of water in blue vitriol is calculated as (90.08 g/mol / (159.61 g/mol + 90.08 g/mol)) × 100, which is approximately 36.1%.