Refractometers are widely used to measure the amount of dissolved substances in solutions containing mainly sucrose. The relationship between refractive index and the amount of dry substance content is well known for sucrose and is the basis of the BRIX scale, which is the measure of the number of grams of sucrose present per 100 grams of aqueous sugar solution. That is, 50 BRIX means 50 grams of solid per 100 grams of solution. This relationship holds for a large number of similar substances and so the BRIX scale is widely used in the food industry. Unfortunately the refractive index of a sugar solution changes with temperature while its solid content remains the same.