Measurement and Modeling of Refractive Indices for Multicomponent Chromium Compound Solutions

Abstract

The aim of this work is to solve the key problems of the green production process for chromium trioxide and to study the thermodynamic properties of corresponding solutions. The refractive indices of quaternary mixtures (chromium trioxide + potassium chromate + potassium dichromate + water) have been measured from 298.15-333.15 K. A molecular thermodynamic model of refractive indices for aqueous solutions of chromium compounds is proposed, based on the author's molecular model for solution structure and an equation for the excess enthalpy of a binary solution obtained from the experimental measurements. The model parameters are confirmed and quantitative equations for the variation of the model parameters with temperature and the molality of potassium dichromate in the mixed solvent are established. The data predicted by the model are in good agreement with the experimental results.

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−

“…Moreover, the molar refraction was in agreement with the data calculated from Equations (1) and (2) using the density and refractive index from [6] (r 2 = 0.9941 and S.E. = 0.0030 cm 3 •mol −1 ). Figure 1 shows the results obtained.…”

“…They also calculated the polarizability of the cations Na + , K + , Rb + , Cs + , Ca 2+ , Ba 2+ , and Sr 2+ and the anions F − , Cl − , Br − , I − , ClO4 − , NO3 − , and SO4 2− . Wang et al [3] proposed a molecular model to represent the refractive index of quaternary aqueous solutions (chromium trioxide + potassium chromate + potassium dichromate + water) at (298.15 to 333.15) K. The results were consistent with the experimental observations. The multicomponent system was considered as a pseudo binary system with chromium trioxide as solute and potassium chromate + potassium dichromate + water as solvent.…”

“…is 0.0063 cm 3 •mol −1 for sodium sulfate, and r 2 is 0.9964 and S.E. is 0.0090 cm 3 •mol −1 for potassium sulfate. The refractive index and molar refraction for the system Li2SO4+H2O were described using the parameters R ∞,0 j and R ∞,1 j.…”

“…is 0.00136, and for the molar refraction, r 2 is 0.9086 and S.E. is 0.0446 cm 3 •mol −1 . This shows that n and R are affected by temperature and salt concentration changes, as can be seen in Figure 3a,b.…”

“…It is defined as the ratio of the speed of light in a vacuum to its speed in that medium [1]. This property is useful to determine the concentration of compounds in liquid solutions and to study optical properties in film and fiber optic technologies, thermodynamic properties, molecular polarizability, and molecular interactions in liquid solutions, among others [2,3]. The refractive index could be also applied for monitoring industrial processes where the control variable is the concentration of the target compound in the solution [4,5].…”