Aqueous ammonium thiocyanate solutions as refractive index-matching fluids with low density and viscosity

TL;DR

This paper demonstrates that aqueous ammonium thiocyanate solutions can serve as effective, low-density, low-viscosity refractive index-matching fluids for optical experiments, with models for their properties and compatibility analysis.

Contribution

It introduces empirical models for the optical and physical properties of ammonium thiocyanate solutions and assesses their chemical compatibility for experimental use.

Findings

Solutions match refractive index of common materials

Low viscosity and density compared to other fluids

Chemical compatibility with typical experimental materials

Abstract

We show that aqueous solutions of ammonium thiocyanate (NH4SCN) can be used to match the index of refraction of several transparent materials commonly used in experiments, while maintaining low viscosity and density compared to other common refractive index-matching liquids. We present empirical models for estimating the index of refraction, density, and kinematic viscosity of these solutions as a function of temperature and concentration. Finally, we summarize the chemical compatibility of ammonium thiocyanate with materials commonly used in apparatus.