As of 1 April 2026, the PSJD database will become an archive and will no longer accept new data. Current publications from Polish scientific journals are available through the Library of Science: https://bibliotekanauki.pl
A new optical method for measuring the optical activity of crystals is developed. Temperature dependence of gyration component g_{11} of ferroelectric lead germanate is measured. The obtained results confirm that lead germanate may be considered as a gyroelectric crystal.