Determination of the Gyration Tensor Components of Ammonium Rochelle Salt

The absolute optical chirality of sodium ammonium (+)‐tartrate tetrahydrate crystals has been determined. The wavelength dispersion of the linear birefringence and the optical gyration tensor components were found at room temperature with the use of a high‐accuracy universal polarimeter. The wavelength dispersion of the gyration is presented over the range 350–650 nm. The gyration coefficients at a wavelength of 500 nm were found to be g 11 = 12.5 × 10 −6 , g 22 = −36.0 × 10 −6 and g 33 = 6.7 × 10 −6 . The results of the present work are in good agreement with values inferred by Koralewski & Szafrański [ Ferroelectrics (1988), 80 , 269–272].