MEASUREMENT OF THE POLARIZATION (OPTICAL- ROTATION) OF WHITE SUGAR - DESCRIPTION OF A MODIFIED METHOD AND COLLABORATIVE TESTS

The normal procedure of measuring the polarization (optical rotation), viz. preparing a soilution of the normal weight of the sample in a vo lumetric flask, is subject to statistical and systematic errors which arise from the step of filling up the flask to the mark and which impa ir the inherent precision of the optical measurement. For the investig ation of white sugars these errors can be avoided by weighing the solu tion and calculating a volume correction on the basis of the known den sity of sucrose solutions. The procedure is described and the improvem ent of the results demonstrated by a collaborative study carried out f or the 20th Session of ICUMSA held in 1990. A method description along the lines of recommendations of IUPAC is given.