Electrogyration effect of Rb2ZnCl4

Electrogyration effect in the incommensurate phase of Rb 2 ZnCl 4 , which had been found to be optically active, was studied. Three plates, (010), (001) and (011), were subjected to HAUP measurements. On (010) and (001) plates no electrogyration effects were observed. On a (011) plate we observed that a linear electrogyration coefficient μ 41 takes place just above T c . A quadratic coefficient μ 41 displays two remarkable peaks at a point 3°C below T i and T c . The upper peak of μ 41 is similar to the one observed in [N(CH 3 ) 4 ] 2 ZnCl 4 . It is of interest that both crystals belong to the same class in our new classification of optical activity.