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Effect of Ionic Strength on Acid-Base Properties of Vicinal Water

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Abstract:Surface research over the past 75 years has clearly shown that water under the influence of electrical and magnetic force fields (vicinal water) does not have the same properties as bulk water. Vicinal water is vital in influencing and maintaining the critical spatial and conformational intramolecular relationships in macromolecules. If the structure of the water molecule changes, it may not positively influence the conformation, chemical reactivity, and function of the macromolecule.
Our objective was to determine the thermodynamic activity of both innersphere and outersphere water surrounding metal cations. Stock solutions of Li- and CaNO3 were made up having a minimum purity of 99.995%; metal concentrations used were:
9 M, 5.24 M, 3.4 M, 1.9 M, 1.1 M, and 0.6 M. Near-infrared spectroscopy monitored the change in the OH vibrational peaks of the H2O molecule as a function of cation type and ionic strength. The scan range was 4000- 8000 cm-1. For CaNO3 the band at 4400 cm-1 was attributed to innersphere water while the band at 5200 cm-1 is attributed to bulk water. For LiNO3 the O-H band at 7200 cm-1shifted up field, and the absorbency decreases as the metal concentration increases. Ultra-violet spectroscopy and an organic molecular probe were used to measure the Lewis acid-base character of vicinal water. The breaking of the O-H bonds created free protons in the presence of an organic Lewis base, resulting in the formation of a monovalent cation. Solution driven acid-catalyzed hydrolysis was not observed. We conclude that the water activity was lowered due to the elevated salt concentrations, and that proton activity was enhanced. The decrease in activity lowered the strength of the O-H bonds, causing them to have a higher dissociation constant. Three different types of water were observed, innersphere water, outersphere water (water bonded to water), and free water.
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Citation:Galloway, J. R., and G. W. Bailey. Effect of Ionic Strength on Acid-Base Properties of Vicinal Water. Presented at Annual Biomedical Research Conference for Minority Students, San Diego, CA, October 15-18, 2003.
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Contact: Janice Sims - (706) 355-8011 or sims.janice@epa.gov
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Division: Ecosystems Research Division
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Branch: Processes & Modeling Branch
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Product Type: Abstrct/Oral
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Presented: 10/15/2003
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Related Entries:
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Bullet Item Developing Computational Tools for Predicting Chemical Fate, Metabolism, and Toxicity Pathways
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Last Updated on Monday, October 22, 2007
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