Inorganic ions are usually classified as structure makers or structure breakers according to the viscosity B-coefficients of their aqueous solutions at ordinary temperature. Structure-making ions enhance the hydrogen bond strength while structure-breaking ones weaken the hydrogen bonds in aqueous solution. We here show that even structure-making ions (assigned by their viscosity B-coefficients at ordinary temperature) become a structure breaker in the sense that they weaken the hydrogen bonds in aqueous solution at low temperatures when we compare the strength of hydrogen bonds with that for glassy water. (c) 2006 Elsevier B.V. All rights reserved.