Rotation of the polarisation plane through sugar solutions

Experiment C3.3.4.1 demonstrates that optically active substances can rotate the plane of a linerally polarised beam of light by a specific value. For a given cuvette length d, the angle of rotation α of an optically active solution is proportional to the concentration c of the solution.

To determine the concentration c of the solution, the following expression applies:

specific rotation: [α] (°· ml/g · dm)

The angle of rotation is given as a positive (+) value when the polarisation plane of the light directed toward the observer rotates clockwise (to the right). Counterclockwise rotation is referred to as rotation to the left and expressed as a negative number, hence preceded by a minus sign (-).