A hand refractometer is used to measure the refractive index, Brix, or other concentrations of liquid, viscous, and even pasty samples. It works by measuring the amount that light is bent refracted when it passes from the air into a sample.
A hand refractometer is primarily used for quality control and production purposes, such as determining the purity of substances. In the food and beverage industry, for example, a hand refractometer can be used to measure the sugar content (Brix) of fruit juices and concentrates, carbonated beverages, jams, confectionaries, and much more. Winemakers, however, rely on hand refractometers to measure the Oechsle of grape must in vineyards to determine the optimal harvesting time during winemaking.
In the chemical industry, hand refractometers are used to verify the concentration value of acids, bases, or the presence of organic solvents in inorganic salt (% w/w or v/v). Meanwhile, in the pharmaceutical industry, they are typically used for controlling the purity and concentration of raw materials, semi-finished products, and end products.