NMR Studies of Aqueous Electrolyte Solutions. III. Hydration of Sodium Perchlorate, Hydrochloric Acid, and Perchloric Acid from Temperature Effects on Proton Shifts

Proton resonance shifts of aqueous solutions of NaClO4 and HCl are measured as a function of temperature and concentration. In each case the proton spectrum consists of a single resonance line which is sensitive to both temperature and concentration. The shift is considered to be an average of the proton in its various environments; namely, bulk water and ionic hydrates. At low concentrations the total hydration numbers of NaClO4, HCl, and HClO4 are determined to be 3.0 ± 0.2, 3.4 ± 0.4, and 2.6 ± 0.4, respectively. Assignments of individual hydration numbers to H+, Na+, Cl−, and ClO4− ions are discussed.