Accurate Determination of Ion Polarizabilities in Aqueous Solutions

Abstract

We present a novel method for obtaining salt polarizabilities in aqueous solutions based on our recent theory for the refractive index of salt solutions, which predicts a linear relationship between the refractive index and the salt concentration at low concentrations, with a slope determined by the intrinsic values of the salt polarizability and the density of the solution. Here we apply this theory to determine the polarizabilities of 32 strong electrolyte salts in aqueous solutions from refractive index and density measurements. Setting Li + as the standard ion, we then determine the polarizabilities of seven cations (Na + , K + , Rb + , Cs + , Ca 2+ , Ba 2+ and Sr 2+ ) and seven anions (F − , Cl − , Br − , I − , ClO − 4 , NO − 3 and SO − 4 ), which can be used as important reference data.We investigate the effect of temperature on salt polarizabilities, which decreases slightly with increasing temperature. The ion polarizability is found to be proportional to the cube of bare ionic radius (r 3 bare ) for univalent ions, but the relationship does not hold for multivalent ions. Contrary to findings of Krishnamurti, we find no significant linear relationship between ion polarizability and the square of the atomic number (N 2 ) for smaller ions.

Thermoresponsive behavior of poly[trialkyl-(4-vinylbenzyl)ammonium] based polyelectrolytes in aqueous salt solutions

“…3, since the order of the ionic radii of the anions follows the order 75 The polarizability of an anion is proportional to its size: larger anions are more polarizable. 74,75 However, the reversed Hofmeister series is not completely followed for PC2N as it has been shown that for PNIPAm that LiNTf 2 acts like a strong kosmotrope for PNIPAm. 50 Nevertheless, LiNTf 2 has the strongest effect for PC2N (Fig.…”

“…This is clearly visible from the fact that H 2 PO − than either of the latter ions. 75,77 Thus, anion polarizability cannot be the only determining factor for the strength of interaction between PC3N and the anion in all cases. Na 2 CO 3 (up to 2.0 M) and Na 2 SO 4 (up to 1.8 M) were also tested with PC3N, but no transition was observed, and it is possible that the reversed Hofmeister behavior is not followed for these two salts.…”

Modeling of the Refractive Index for the Systems MX+H2O, M2X+H2O, H3BO3+MX+H2O, and H3BO3+M2X+H2O. M = K+, Na+, or Li+ and X = Cl− or SO42−

“…Li et al [28] estimated the polarizability of LiCl, NaCl, NaBr, KBr, and Na2SO4 in mixed solvents (water + acetonitrile and water + ethanol). For this purpose, they extended their model reported in [1,23]. The ion polarizability of Na + , Cl − , and Br − in the mixed solvents was reported.…”

“…An et al [1] proposed a theoretical equation to describe the refractive index for binary salt solutions (NaCl, KCl, NaBr, and KBr) and water + acetonitrile + salt solutions at 298.15 K, obtaining good results, particularly at low salt concentrations. Li et al [23] presented a method to estimate the polarizability of the ions from their refractive index in water. This method was based on their previous theoretical equation [1].…”

Enhancement of Ion Pairing of Sr(II) and Ba(II) Salts by a Tritopic Ion‐Pair Receptor in Solution

“…[80], we calculate μ CIP , μ SIP , A CIP, and A SIP (Table S3, SI) using data for ionic radii, solvent radii, and polarizabilities from Refs. [81][82][83]…”