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Feb 11, 2014 - Near infrared spectral studies of aqueous solutions of metal perchlorates in groups. I A, II A, II B, III A and III B of the Periodic. Table. Anna G.

A.G. Davidian et al., J. Near Infrared Spectrosc. 22, 27–34 (2014) Received: 22 September 2013 n Revised: 11 February 2014 n Accepted: 21 February 2014 n Publication: 3 April 2014

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JOURNAL OF NEAR INFRARED SPECTROSCOPY

Near infrared spectral studies of aqueous solutions of metal perchlorates in groups I A, II A, II B, III A and III B of the Periodic Table Anna G. Davidian,* Andrey G. Kudrev, Lyubov A. Myund and Maria K. Khripun Chemistry Department, Saint-Petersburg State University, Universitetsky pr. 26, Stary Peterhof, Saint-Petersburg 198504, Russian Federation. E-mail: [email protected]

Chemometrics of NIR spectra of aqueous salt solutions M(ClO4)n, where M n+: Li+, Na+, Mg2+, Ca2+, Sr2+, Ba2+, Zn2+, Cd2+, Al3+, Ga3+, In3+, Sc3+, Y3+, La3+ were used to establish the effect of the cation nature on the structure of aqueous electrolytes solutions. Principal component analysis showed that near infrared (NIR) spectra of the systems under study are grouped into clusters. It was found that the values of the eutectic concentrations of aqueous salt solutions and the polarising powers of cations correlate. The combined use of NIR spectroscopy, chemometrics of the spectral data and a generalised phenomenological model of the structure of aqueous electrolytes solutions is a new approach to studying of the structure of concentrated solutions. Keywords: NIR spectra, aqueous solutions, metal perchlorates, principal component analysis, polarising power of a cation, eutectic concentration­

Introduction A common method for studying the water state in a solu- established that the first hydration sphere of water molecules forms strong hydrogen bonds to the second sphere and the tion is infrared (IR) spectroscopy. Subramanian and Fisher1 reported near infrared (NIR) spectra of sodium, magnesium, second-sphere water molecules of these trivalent cations form hydrogen bonds to outer water, which are comparable zinc and aluminium perchlorates in the region of the first in strength to those formed by the first-sphere water moleovertone of water. In this paper1 the effect of the perchlorates cules of divalent cations. Chen et al.3 examined the ATR-FTIR of sodium, magnesium, zinc and aluminium on the structure of water was studied with respect to the effects of anions, spectra of aqueous NaClO4, LiClO4, Mg(ClO4)2 solutions with cations, concentration and temperature. The anions play the ClO4– concentrations ranging from 0 mol L−1 to 3 mol L−1. The predominant role, whereas the effect of cations is found to be “structure breaking” effect of perchlorate ions on the hydrogen only of secondary importance. The IR spectra of aluminium, bond network of water and the “structure making” effect of chromium and rhodium perchlorates in both the OD (2900– the three cations, which is consistent with the ability of the 1800 cm−1) and OH (4000–2800 cm−1) stretching regions were polarisation and hydration in the order of Na+ 

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