Infrared optical constants of aqueous solutions of electrolytes. Alkali halides

Abstract

The normal-incidence spectral reflectance of aqueous solutions of alkali halides has been measured in the spectral range 350-5000 cm™1. From the measured values of reflectance we have used Kramers-Kronig phase-shift analysis to provide values of the real and imaginary parts of the complex refractive indices Ñ = n + ik of the solutions. The plots of k(v) vs. v give quantitative measures of absorption band intensities as well as positions; we find that the negative ions produce greater changes in the absorption spectrum of the solvent than do the positive ions. Similarly, we find that the negative ions have greater influence on n(v) in the near infrared; all the halide ions increase n(y) to values above that of water but, at a common concentration, the iodide ion has the greatest effect. The primary influence of the ions on n(v) in the near infrared can be attributed to electronic bands in the ultraviolet. The influence of the ions on the characteristic water bands is related to the influence of the ions on the intermolecular structure of water. Publication costs assisted by Environment CanadaThe laser Raman spectra of aqueous MgS04 solutions have been recorded at pressures up to 1 kbar for temperatures between 7.0 and 25.0°. The results are used to calculate the volume changes of dissociation of MgS04°c ontact ion pairs (average V = -20.3 ± 1.4 cm3 mol'1 between 7.0 and 25.0°). The absence of temperature dependence of AV and the different values of V obtained by other techniques are discussed in terms of a multistate ion pair equilibrium process.

Infrared Spectroscopic Properties of Sodium Bromide Aerosols

“…Indeed, the band center of 4 mol/L NaBr solutions is located ∼10 cm -1 wavenumbers higher than the band center of pure liquid water. 30 The same trend is observed for NaCl solutions, 41 showing a 33 cm -1 shift between NaCl solution at 5 mol/L and pure water.…”

“…For spherical particles, Q scat and Q ext can be computed exactly using Mie theory. 27 We have calculated b scat and b ext for NaBr particles, taking optical constants from Li 29 (solid) and Rhine et al 30 (4 M aqueous solutions). For solid NaBr, k can be taken to be zero from 1000 to 4000 cm -1 (i.e., solid NaBr particles will not absorb light in this region).…”

“…The integral extends over the OH asymmetric stretch absorption band (in our case, from 2800 to 3600 cm -1 ). Although it is best to use k of NaBr aqueous solutions, 30 a rough estimate may be obtained from pure water data 32 To determine the NaBr solute content of the aerosols, a filter was inserted at the exit of the flow tube to collect dry aerosol particles in a given time interval. A membrane vacuum pump was used to increase the flow.…”

H3O+ ions in aqueous acid solutions. The infrared spectra revisited

“…On the corltrary, their spectra, like ours, show a rnininnurn of the absorption coeecient near 1200 cm-I. As for the v2 band of water, it is shifted, if at aii, to lorzter frequency in solutions of electrolytes (15). Whatever the origin of these extraneolus features, the conclusion derived from them is obviously unfounded.…”

Spectral Radiative Properties of a Liquid n-Octane Droplet in the Midinfrared Region

“…With the development of experimental conditions, numerous experimental approaches have been proposed to investigate the optical properties of liquids, such as the attenuated total reflection (ATR) method [16][17][18][19][20], the transmission method [21][22][23][24], the combined transmissionreflection method [25,26], and the ellipsometry method [27][28][29][30][31][32][33]. e ATR method is suitable for the measurement of absorption indices in strong absorption regions, whereas the transmission method is especially suitable for measuring the absorption indices of liquids in weak absorption regions.…”