Principles
of Refractometry
Refractometers are
instruments used to measure substances dissolved in water and certain
oils. The refractometer works using the principle of light refraction
through liquids. As light passes from air into a liquid it slows down.
This phenomenon is what gives a "bent" look to objects that
are partially submerged in water.
To put it simply, the more dissolved solids
water contains, the slower light travels through it, and the more
pronounced the "bending" effect on light. Refractometers use
this principle to determine the amount of dissolved solids in liquids by
passing light through a sample and showing the refracted angle on a
scale. The scale most commonly used is referred to as the Brix scale.
The Brix scale is defined as: the number of grams of pure cane sugar
dissolved in 100 grams of pure water (grams sugar/100 grams H20).
Other scales have been developed to measure salt, serum proteins
(albumen) and urine specific gravity.
