Spectrometric studies of sodium perchlorate contact ion-pair formation in aqueous solutions

Technical Report · Mon Nov 01 04:00:00 EST 1982

OSTI ID:6713735

Miller, A G; Franz, J A; Macklin, J W

It is concluded that concentration-dependent variations in the perchlorate ion analytical line, nu/sub 1/(A/sub 1/), are caused by the presence of contact ion pairs and, to a lesser extent, solvent-separated ion pairs of NaClO/sub 4/. Spectroscopic studies indicate a linear dependence between contact association and sodium molality. The estimated thermodynamic association constant is 0.022m/sup -1/, which compares to 1.22 for the thermodynamic exchange equilibrium constant for ClO/sub 4//sup -/ ion displacing one water molecule from sodium. Na/sup +/ ions have little preference for ClO/sub 4//sup -/ over water, and only at high concentrations, where water content is low, will extensive contact association take place. The interaction is also weak. These conclusions are supported by the smaller splitting of the perchlorate nu/sub 2/(E) band relative to aprotic organic solutions, small NMR chemical shifts, and little increase of viscosity-corrected relaxation rates with increasing concentrations. Evidence that perchlorate ion forms weak hydrogen bonds with water is found in Raman, IR, and NMR spectroscopy. Two such hydrogen bonds to perchlorate oxygen atoms being replaced by a sodium ion partially account for the smaller splitting of the nu/sub 2/ band observed in spectra of protic solvents compared to splitting in spectra of aprotic solvents, and for weaker splitting of the perchlorate nu/sub 2/ band in the Raman spectrum than for solutions not containing molar hydroxide levels. They also account for the very small /sup 35/ClO/sub 4//sup -/ chemical shift and viscosity-corrected relaxation rates for /sup 35/ClO/sub 4//sup -/ chemical shifts. These effects support the concept of stronger perchlorate-water hydrogen bonds when hydroxide ion is present than when it is not. 25 figures, 13 tables.

• Research Organization: Rockwell International Corp., Richland, WA (USA). Energy Systems Group; Pacific Northwest Lab., Richland, WA (USA); Washington Univ., Seattle (USA). Dept. of Chemistry
• DOE Contract Number: AC06-77RL01030
• OSTI ID: 6713735
• Report Number(s): RHO-SA-88-Rev.1; ON: DE83003288
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400201* -- Chemical & Physicochemical Properties
ALKALI METAL COMPOUNDS
AQUEOUS SOLUTIONS
CHEMICAL PROPERTIES
CHEMICAL SHIFT
CHLORINE 35
CHLORINE COMPOUNDS
CHLORINE ISOTOPES
DISPERSIONS
HALOGEN COMPOUNDS
ION PAIRS
ISOTOPES
LIGHT NUCLEI
MAGNETIC RESONANCE
MIXTURES
NUCLEAR MAGNETIC RESONANCE
NUCLEI
ODD-EVEN NUCLEI
OXYGEN COMPOUNDS
PERCHLORATES
RESONANCE
SODIUM COMPOUNDS
SODIUM PERCHLORATES
SOLUTIONS
SPECTROSCOPY
STABLE ISOTOPES
THERMODYNAMICS