An optical apparatus designed for the mapping of binary
or ternary phase diagrams is described. A polychromatic polarized
light illuminates a sample and the rotation of its polarization is
measured with a spectrometer for various magnetic fields. The
measured parameters are the natural and magnetic rotatory power of
the sample which allow the concentration retrieval of every
compound to be done. Results show that the apparatus is
suitable for correct positioning of single phase boundary on the
ternary water - n-dodecyl-β-d maltoside - sodium chloride
system.