Electrogyration effect in alums

The electrogyration effect in 31 alums has been measured within the range 350 to 700 nm. The coefficients of electrogyration show an unexpectedly wide variation in alums of different composition and structural type. The effect is obviously related to the symmetry of the constituents and to their bonding interaction with water molecules. The dispersion of the electrogyration can be described by a formula which is also valid for natural optical activity. In contrast to other electro-optical effects Miller's rule does not apply for the electrogyration of the alums.