ABSTRACT
An optical liquid is a liquid whose optical properties are critical to an application. Microscope immersion oil is a good example of an optical liquid. The properties to be considered when choosing an optical liquid are usually more extensive than when choosing optical glasses because liquids are more active, requiring properties such as viscosity, toxicity, and compatibility to be considered. The optical properties of liquids are calculated as if they were homogeneous solids like optical glasses using the same mathematical formulas. The wavelength dispersion of the refractive index of optical liquids can be described mathematically by a Cauchy, Sellmeier, or by a dispersion equation generated from refractive index values measured at several wavelengths. The stability of optical liquids can be analyzed from the standpoint of various destabilizing effects. Other physical properties that might be important and should be considered are pH or neutralization equivalent, fire point, thermal conductivity, and velocity of sound.
