Refractometry models for compositional analysis of binary and ternary mixtures

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University of Pretoria

Abstract

A review of existing compositional binary mixture models for refractive indices was undertaken and showed that they can be recast in forms that are linear in mole or volume fraction. Typically, mole fractions proved to be the better composition descriptor when analysing literature data and the molar refraction was shown to be virtually temperature independent. Depending on whether temperature, density or refractive index measurements of the mixture are available, different correlations were developed to predict the composition (as shown below). Furthermore, refractive index measurements on mixtures of n-alkanes with DEET were taken to determine phase equilibrium behaviour. With extrapolation to infinite molar mass, these alkanes approach polyethylene, which is the material from which DEET-containing mosquito-repellent devices were made. The results show that the microporous structure was likely formed by liquid-liquid phase separation. Lastly, it was shown that Padé approximants provide good representations of binary and ternary refractive index data. The temperature dependence of the pure components was elegantly subsumed in a pure component property, namely, the molar volume. Various constraints were applied to reduce the number of adjustable parameters even further and this proved to be successful.

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Dissertation (MEng (Chemical Engineering))--University of Pretoria, 2024.

Keywords

UCTD, Sustainable Development Goals (SDGs), Refractive index, Polymer solution, Phase equilibrium, N-alkanes, Mixing rules

Sustainable Development Goals

SDG-09: Industry, innovation and infrastructure

Citation

Pretorius, F (2024) Refractometry models for compositional analysis of binary and ternary mixtures, Dissertation, Department of Chemical Engineering, University of Pretoria