Intracrystalline Site Preference of Hydrogen Isotopes in the Water of Crystallization of Copper Sulfate Pentahydrate

Article abstract of DOI:10.1021/j150607a014

Difference in the isotopic partition at the water of crystallization of CuSO4*5H20 (the site preference) was estimated for the hydrogen isotopes.Fractional dehydration of CuSO4*5H2O under vacuum at 0 and 25 deg C was used to determine the isotopic ratio, the amount of dehydrated water, and the rate process of dehydration.The following results were obtained. (1) Two maxima occur in the isotopic ratio in the dehydration range, F<0.8. (2) The dehydration occurs by the three sequential zeroth-order rate processes which have different rate constants for dehydration.The three different rate constants may be explained by the combination of the rate constants of dehydration of the water molecules dehydrated.The estimation of the difference in hydrogen isotope distribution for different sites, i.e., four of five water molecules in the coordination sphere of copper ion (site A) and one bonded to the sulfate ion through hydrogen bonding (site B) was made.The site preference of hydrogen isotopes (δD.<*>) was concluded to be -32.0+/-5.2 for site A and +22.6+/-20.9 for site B, where the δD value was referred to the isotopic ratio of the mother liquor from which the crystal formed.