With a refractometer, the so-called refractive index of a medium is determined by an optical measurement. The refractive index (n) is a quantity which relates the propagation velocity of light in a medium (cM) to the propagation velocity of light in vacuum or also the speed of light in vacuum (C0), which is defined as 1. Differential refractometry is a robust methodology that enables universal detection and has been accepted and established for many years.
Advantages: low price, easy handling, good linear behavior, universally applicable
Disadvantages: lower sensitivity than other universal detectors, not gradient-compatible