Crystal chirality of the non-chiral inorganic salt, α-Ni(H2O)6·SO4

Solid phase circular birefringence (CB = optical rotatory dispersion) and circular dichroism (CD) spectra of α-Ni(H2O)6·SO4, which exhibits optical activity only in the crystalline state, were studied in the 250–600 nm region. A method was devised to remove signals which arise from linear birefringence (LB) and linear dichroism (LD) and give pure CB spectra by using a specially constructed universal chiroptical spectrophotometer. Even in the cases where LB is substantial, the pure CB and CD spectra thus obtained were shown to satisfy the Kramers–Kronig relationship in the 3A2g→3T1g(P)Ni d–d transition region, as do chiral compounds in isotropic medium.