GB715057A - Improvements in or relating to polarimetric apparatus - Google Patents

Abstract

715,057. Polarimeters. KESTON, A. S. Nov. 16, 1951. [Aug. 6, 1951], No. 26907/51. Class 97(1) [Also in Group XL(b)] A polarimeter comprises polarizing means for producing consecutively or simultaneously two beams of plane polarized light the planes of polarization of which are inclined to the extinction plane of an analyser and on opposite sides respectively of said plane, the substance to be tested being placed in the beams before reaching the analyser, and photometric means provided for measuring the intensities of the two beams transmitted by the analyser. The effect of the substance to be tested is to rotate the plane of polarization of one beam away from the extinction plane of the analyser, and that of the other beam towards such extinction plane and the ratio of or difference between the intensities of the transmitted beams gives a measure of the amount of rotation produced by the said substance. In the form shown in Fig. 1 light from a source 11 is plane polarized by a Nicol prism 13. passes through a cell 15 containing the substance under test, through an analyser 14 crossed with the polarizer and reaches a photometer 20 such as a photo-electric cell. A member 16 bears polarizing elements 17 and 18 which respectively rotate the plane of polarization of the beam from the polarizer 13-through small angles in opposite directions, and may slide or rotate to bring one or other of these elements into the beam, the intensities of the resulting beams being measured by the photometer 20. Alternatively the elements 17, 18 may remain stationary, two beams being produced by the polarizer 13, or the elements may be replaced by an electrical arrangement for rotating the polarization plane. Alternatively, the elements 17 and 18 may be omitted the polarizer 13 replaced by two fixed or sliding polarizers which are slightly rotated relative to the plane of extinction of the analyser. In a further modification the polarizer may be fixed and two analysers, rotated relative to the extinction plane, may be slid successively into the beam therefrom. In the modification shown in Fig. 6 polarizers 103 and 104 slightly rotated in opposite directions from the extinction planes of analysers 105 and 106 are slidable, together with the analysers, across the beam from a source 101 passing through the specimen 108. the intensities of the two beams thus produced being measured by the photometer 110.