Refractometer
（重定向自Refractormeter）
![](/Images/godic/202502/06/FIP-Refraktometer0625.jpg")
![](/Images/godic/202502/06/J457_front_open_IMG_11270625.jpg")
!['Schematic setup of an automatic refractometer: An LED light source is imaged under a wide range of angles onto a prism surface which is in contact with a sample. Depending on the difference in the refractive index between prism material and sample the light is partly transmitted or totally reflected. The critical angle of total reflection is determined by measuring the reflected light intensity as a function of the incident angle - Source of image: Anton Paar GmbH, www.anton-paar.com](/Images/godic/202502/06/Measuring_Principle_v20625.png")
![Modern Automatic Refractometers - Source of image: Anton Paar GmbH, www.anton-paar.com](/Images/godic/202502/06/D22IF003-Abbemat_Family_010625.jpg")
A refractometer is a laboratory or field device for the measurement of an index of refraction (refractometry). The index of refraction is calculated from Snell's law while for mixtures, the index of refraction can be calculated from the composition of the material using several mixing rules such as the Gladstone–Dale relation and Lorentz–Lorenz equation.