ISO 2173:1978

The method is particularly applicable to thick products, to products containing suspendes matter and to products rich in sugars. If the products contain other dissolved substances, the results will be only approximate, nevertheless they may be considered conventionally as the soluble solids content. The principle consists in measuring of the refractive index of a test solution at 20 °C, using a refractometer, and use of tables correlating refractive index with soluble solids contents (expressed as sucrose), or direct reading of the content on the instrument.