How to Read Specific Gravity on a Refractometer

A refractometer is a manual device that uses refractive index properties to measure a fluid specific gravity (ratio of the fluid to water density). The refractive index indicates the speed light uses to travel through liquids compared to the speed light travels through air. When light transfers from the air to a liquid, it slows down and bends. The refractometer focuses this bent light on an internal scale you can read through a magnifying eyepiece lens. This number corresponds to the fluid's specific gravity. Laboratory personnel use specific gravity readings to determine the physical properties of urine and other body fluids during laboratory testing.

Instructions

• 1

  Place a drop of the liquid sample on the refractometer's measuring surface. The measuring surface is typically located underneath a lid in the refractometer, called a ViewPoint Illuminator, that flips up and down. Close the lid.

• 2

  Lift the refractometer, keeping it level, and look through the eyepiece, holding the refractometer with one hand and using the other hand to press the ViewPoint Illuminator (lid) down..

• 3

  Find the point on the internal scale where a contrast line appears. The contrast line shows the difference between a light and dark area.

• 4

  Read the number on the internal scale where the contrast line crosses. This number indicates the fluid's specific gravity.