A refractometer is an instrument used to determine the refractive index of gases, liquids, and translucent solids like gemstones. Liquids are tested for things such as blood proteins, salinity, fluid concentrations, and specific gravity of urine. In veterinary medicine, a refractometer is used to measure the total plasma protein in a blood sample. In gemology, a refractometer is used to help identify gem materials by measuring their refractive index. In home brewing, a refractometer is used to measure the specific gravity before fermentation. National microscope deals in high quality refractometers that can be used in labs, on production lines, in the field or anywhere. Designed to meet the efficiency and accuracy standards, the precision and optical performance of refractometers supplied by National microscope lasts forever.