Editorial Feature

Refractometer - Definition and Applications

A refractometer is an optical device used for measuring the extent to which light is bent, or refracted when it moves through a substance. It works because light travels at different velocities in different mediums.

Refractometers are designed for specific operations, such as measuring liquids such as oils, or water-based liquids, gases, and transparent or translucent solids, such as gemstones. In farming, for instance, the refractometer uses the refractive light passing through plant sap, or fruit or vegetable juice, to obtain nutrient levels.

Refractometers are mostly used to determine the index of refraction of liquid samples, and to measure fluid concentrations, such as blood protein concentration, sugar content, and salinity.

Other functions of the refractometer Include:

  • Helping to determine the identity of a sample by comparing its refractive index to previously known values
  • Assessing the purity of a sample by comparing its refractive index to the value for the pure substance
  • Determining the concentration of a solute in a solution by comparing the solution's refractive index to a standard curve

Types of refractometers

The four main types of refractometers are:

  • Traditional handheld refractometers
  • Digital handheld refractometers
  • Laboratory refractometers
  • Inline process refractometers

Automatic refractometers have also been developed. These are microprocessor-controlled electronic devices that can be combined with other measuring devices.


The following are some of the key applications of refractometers:

  • Drug diagnosis
  • Gemology
  • Veterinary medicine
  • Aquarium upkeep
  • Farming

Sources and Further Reading


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