Refractive index measurement of sol forming Laponite JS dispersion using interferometry

• Proposed a method for refractive index measurement Laponite JS dispersion
• Mach–Zehnder interferometer is used together with an Abbe-refractometer.
• Refractive index of the dispersion decreases with temperature.
• Refractive index of the dispersion increases with concentration.
• Extended Lorentz–Lorenz equation fits the refractive index variation very well.

In this work refractive index (RI) of a solution (sol) of water-dispersed Laponite JS has been experimentally measured by using the Mach–Zehnder configuration of an interferometer combined with an Abbe-type refractometer. It was observed that the RI of the Laponite JS dispersion increases with an increase in Laponite concentration while it decreases with increasing temperature. The behavior of RI as a function of density was observed to be in good agreement with the extended Lorentz–Lorenz equation. It suggests that changes in RI arising from the temperature are mainly accounted for through the change in density while the direct effect of temperature being small. Finally, RI of the sol forming Laponite JS dispersion was compared with the previously reported data of the gel forming dispersion of Laponite RD and was found to be in qualitative agreement.

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