A SIMPLE AND RELIABLE SYSTEM FOR MEASURING THE REFRACTIVE-INDEX OF LIQUIDS USING A POSITION-SENSITIVE DETECTOR

A simple and yet efficient apparatus for the measurement of the refrac tive index of liquids has been developed, with the purpose of controll ing adulteration in liquids of everyday use. In the system, the index of refraction of the liquid under test is determined by measuring the lateral displacement of a laser beam, that passes obliquely through a rectangular cell filled with the liquid under characterization. The la teral displacement is accurately determined by a position-sensitive de tector. A careful analysis of the errors that can be obtained with the system has been carried out, tha t yeilded calibration curves for eas y on-line correction. To characterize the performance of the system, a series of tests has been performed on simple liquids, under controlle d conditions. The residual errors have proven to be within one part ov er 10(3). The proposed system is suitable for easy automation, obtaini ng simple and accurate measurements that can be performed also for vol atile compounds.