A new optical method and apparatus `HAUP' for measuring simultaneously optical activity and birefringence of crystals. II. Application to triglycine-sulphuric acid (NH₂CH₂CO₂H)₃.H₂SO₄

As the test for the utility of HAUP, simultaneous determinations of birefringence, optical activity, and rotation of the indicatrix, and electrooptic, and electrogyration coefficients were made for both paraelectric and ferroelectric states of triglycine-sulfuric acid, 3C₂H₅NO₂.H₂SO₄. In the ferroelectric state, the hysteresis loop of the gyration tensor g₂₂ was clearly observed. Electrooptic and electrogyration coefficients referred to polarization are found to be nearly independent of temperature over the paraelectric and ferroelectric states. It is important to note that gyration is more largely induced than birefringence under lower electric fields. This fact, contrary to the previous belief, indicates that simultaneous determinations of gyration and birefringence are indispensable for the correct evaluations of the optical properties of crystals.