Refractometer

A refractometer is an optical instrument that measures the refractive index of a liquid or solid sample, the degree to which the material bends light passing through it, a property that can be used to identify a substance or, more commonly, to determine the concentration of a dissolved substance such as sugar, salt or alcohol in a solution. Instruments for measuring refractive index were developed through the nineteenth century, with the German scientist and industrialist Ernst Abbe designing an influential and widely adopted refractometer in the 1870s and 1880s that established a standard laboratory design still recognized in refractometers today. Refractometers are used extensively in the food and beverage industry, for example to measure sugar content in fruit juice, wine and beer production, in the chemical and pharmaceutical industries for quality control, and in gemology, where refractive index measurement helps identify and distinguish gemstones.