refractometer

thumb|Hand-held refractometer A refractometer is a laboratory or field device for the measurement of an index of refraction (refractometry). The index of refraction is calculated from the observed refraction angle using Snell's law. For mixtures, the index of refraction then allows the concentration to be determined using mixing rules such as the Gladstone–Dale relation and Lorentz–Lorenz equation.

== Refractometry == Standard refractometers measure the extent of light refraction (as part of a refractive index) of transparent substances in either a liquid or solid state; this is then used in order to identify a sample, analyze the sample's purity, and determine the amount or concentration of dissolved substances within liquid samples. As light passes through the liquid from the air, it will slow down and create a ‘bending’ illusion. The severity of the ‘bend’ will depend on the amount of substance dissolved in the liquid. For example, the amount of sugar in a glass of water.