Abstract: A device for calibrating an instrument that measures circular dichroism has a transparent dielectric plate rotatably mounted in a framework so as to be rotatable about an axis passing through the plate substantially normal to the main irradiation direction, and means for indicating the angular position of the plate relative to its axis of rotation. A quarter-wavelength plate is mounted on the framework spaced from the dielectric plate with a surface normal to the irradiation direction.

Abstract: The conformation of optically active molecules is investigated by projecting a monochromatic and unpolarized beam of light into a sample cell containing such molecules for causing the latter to luminesce, providing optical modulating means for intensity modulating polarized light in the radiation incident on the modulating means, beaming a portion of the luminescent output of the sample cell on the modulating means in such a way as to minimize the amount of linearly polarized light incident on the modulating means, and measuring the intensity of light at a predetermined wavelength emerging from the modulating means. The luminescent output of the sample cell incident on the modulating means contains a small amount of circularly polarized light in the presence of a large amount of unpolarized light.