An Abbe refractometer is an instrument used to measure the refractive index of a liquid, by utilizing the critical angle for total reflection.

Some labs store the refractometer with a piece of tissue in the prism assembly to keep the prism glass from being scratched.

Any of several instruments used to measure the index of refraction of a substance. it is commonly known to be used in wine making, where the refractometer is used to measure the sugar content in the fruit juices.

A refractometer measures the refraction of light through a medium. In beer manufacture it tests for the density of sugars in the beer and is able to tell you the sweetness.

Deionized, distilled water