The refractive index of sugar solutions is used as a rapid method for the approximate* determination of dry substance content. The method can be used with plant juices, syrups, marmalades and jams. In high purity sugar solutions it is used as a measure of sugar content.

*NOTE – For a pure solution of known composition, the refractive index measurement gives the exact dry substance content of the relevant sugar [1].  For technical solutions which have additions of unknown non-sugars, the refractive index measurement gives the dry substance content in a more or less good approximation, depending on the purity of the solution.