Proton NMR studies on concentrated aqueous sulfuric acid solutions and Nafion-H

Sulfuric acid containing limited amounts of water, H₂SO_4.nH₂O with 0.23≤n≤4, has been studied by ¹H broad-line NMR at 4 K and MAS NMR at room temperature. The broad-line NMR spectra indicate the formation of H₃O⁺ and HSO₄ ^- ions. H₂SO_4.2H₂O is correctly written as H₃O⁺HSO₄ ^-.H₂O. The results are compared with the Nafion- H/water system. This revised version was published online in July 2006 with corrections to the Cover Date.