a method for determining the concentration of optically active substances in solutions. The method is applied chiefly to sugars, from which it receives its name. Sac-charimetry is carried out under standard conditions. The scale of the measuring device, known as a saccharimeter, is so calibrated that the concentration of optically active substances can be read as a percentage when the measurement is taken under standard conditions. Sugar concentrations are measured on the International Sugar Scale, where 100 sugar degrees (100S degrees) correspond to the rotation of the plane of polarization of light by an aqueous sugar solution containing 26,000 g of pure sucrose in 100 ml of solution (100S degrees = 34.620 angular degrees). The rotation is measured at 20°C in a tube 200 mm long. Standard conditions also require that sugar solutions be illuminated by white light, although monochromatic light of appropriate wavelength is used in measuring the concentration of other substances, such as camphor. Saccharimetry is widely used in the food-processing and pharmaceutical industries.