For measuring degree of rotation of plane polarized light by solution of optically active substances. The polarizer and rotatable analyzer are positioned along the same horizontal axis in a tube. Circular scale graduated 0-360 X 1°., with a vernier scale of LC 1/10°, mounted along side analyzer with respect to polarizer. Analyzer and vernier scale rotate simultaneously and have locking screw and fine adjustment screw. Central portion of tube has a window for placing a 20cm sample tube inside along the polarized light path, and is painted black inside to minimize internal reflections. Ground glass provided at objective of polarizer for better image contrast. Complete assembly on a heavy tripod stand with adjustable height.