Definition

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  A refractometer is a laboratory apparatus for measuring the refractive index of a substance like water or alcohol. In general, refractometers are utilized to determine the composition and purity of substances quantitatively. The most common types of refractometer are Abbe refractometer, Digital handheld refractometer, Digital benchtop refractometer and Handheld manual refractometer (shown in Figure 1 are some of the types of refractometer, adapted from Cole-Parmer catalog of refractometers).
  
  

Refractive Index

• Figure 2 - Snell's Law
  
  The refractive index is a value obtained by dividing the velocity (distance traveled divided by the time required to travel that distance) of light in a vacuum (empty space) to the velocity of light in a medium (container).
  The refractive index is expressed quantitatively by using an equation derived from Snell's Law (shown in Figure 2 and adapted from HyperPhysics, Index of Refraction).
  
  

Refraction of Light

• Refraction of Light
  
  The refractometer's mechanism of action is derived from the Refraction of Light principle--in other words, the bending of a light's wave when it changes speed upon entering a transparent object (shown in Figure 3 and adapted from HyperPhysics, Index of Refraction).
  
  

Sugar Measuring Tool

• Figure 4 - Brix Scale
  
  A refractometer is a significant tool in measuring the sugar content of foods. It is done by using the Brix scale, which is the measure of soluble sugar in water at a particular temperature. For instance, a sample with a refractive index value of 1.3403 is equal to 5.0 percent sucrose in the Brix scale (shown in Figure 4 is the Brix scale and its equivalent refractive index value, adapted from Cole-Parmer Technical Library).
  
  

Analytical Tool

• Researchers analyze and determine the amount of acids, fats and salt are present in a substance by using a refractometer. For instance, cleaning liquids such as alcohols are analyzed in industrial laboratories to detect the presence of dirt and other contaminants.
  
  

Diagnostic Tool

• A refractometer is a diagnostic tool utilized in clinical laboratories for urinalysis and serum protein content determination. The refractive indices obtained from the samples are compared to a standard scale to obtain an accurate diagnosis.