Dissolved sugar content
Scientists use degrees Brix (symbol °Bx), introduced by Antoine Brix, as units of measurement of the mass ratio of dissolved substance to water in a liquid. A 25 °Bx sucrose solution has 25 grams of sucrose sugar per 100 grams of liquid. Or, to put it another way, 25 grams of sucrose sugar and 75 grams of water exist in the 100 grams of solution.
An infrared Brix sensor measures the vibrational frequency of the sugar molecules, giving a Brix degrees measurement. This does not equate to Brix degrees from a density or refractive index measurement because it will specifically measure dissolved sugar concentration instead of all dissolved solids. When using a refractometer, one should report the result as "refractometric dried substance" (RDS). One might speak of a liquid as having 20 °Bx RDS. This refers to a measure of percent by weight of total dried solids and, although not technically the same as Brix degrees determined through an infrared method, renders an accurate measurement of sucrose content, since sucrose in fact forms the majority of dried solids. The advent of in-line infrared Brix measurement sensors has made measuring the amount of dissolved sugar in products economical using a direct measurement.
Sugar purity
Technicians usually measure the purity of sugar, i.e. the sucrose content, by polarimetry — the measurement of the rotation of plane-polarized light by a solution of sugar.
