GB903988A - Improvements in or relating to methods of and means for measuring optical rotations and optical rotatory dispersions - Google Patents

Abstract

903,988. Photo-electric polarimeters. GLAXO LABORATORIES Ltd. Aug. 26, 1958 [May 30, 1957 (2); Jan. 1, 1958], Nos. 17234/57, 17235/57 and 85/58. Class 40 (3). In a polarimeter, two beams of monochromatic light transversing the test substance, at least one being polarized and at least one being intermittent fall on a photo-sensitive device. Where both beams are polarized they have different planes of polarization. A single beam may be split and interrupted after traversing the test substance, Fig. 3 (Provisional 17234/57) (not shown). As shown in Fig. 1 (Provisional 17234/57) a constantly rotating sector mirror R1 causes light from a source to pass alternately through polarizers F, P and the resulting beams the planes of polarization of which are preferably at 90 degrees to each other are passed on by a further rotary sector mirror R2 the test cell S and an analyzer A, the plane of which is set so as to bisect the planes of the two beams, to a photo-multiplier D. In a similar arrangement, Fig. 2 (Provisional 17234/57), a single polarizer of a double-image kind is used instead of the two polarizers. This arrangement is specially suitable for ultraviolet light. In another arrangement using a double-image polarizer and analyzer, Fig. 3 (Provisional 17234/57) (not shown), the rotary and fixed mirror system is replaced by a single rotary sector shaped shutter. In a similar arrangement, Fig. 4 (Provisional 17234/57) instead of passing both beams from the polarizer alternately to the measuring cell the rotary shutter Z1 operate on one beam only, the other being passed continuously. In all systems masks are provided at appropriate positions to limit the beams ultimately reaching the photocell to two. In further modifications, Figs. 1 and 2 (Provisional 85/58), masks are not used and four beams in alternate pairs may be allowed to fall on the same portion of the sensitive device. To facilitate amplification, the beams may be chopped at a frequency higher than that of the alternations. Where the light source is an arc its position may be automatically stabilized. Where a monochromator is used the wavelength setting may be coupled to the recording means to enable records of the rotary dispersive power of the sample to be made. Construction of rotary shutters and choppers.- As shown in Fig. 3 (Provisional 85/58), two discs 7, 8 are arranged for rotation in opposite directions so that over 180 degrees the outer beams pass through slots 3, 4 and for the remaining 180 degrees the inner beams pass between the discs. In another arrangement, Fig. 4 (Provisional 85/58), for two beams only the discs rotate in the same direction and so allow the beams to pass alternately, the beams also being chopped by the teeth. In another arrangement, Fig. 5 (Provisional 85/58), four beams are passed alternately in pairs and chopped. As a further alternative, the shutters may be in the form of drums with the photo-cell mounted inside or with mirrors mounted inside for reflecting the beams to an external detector, Figs. 6 and 7 (Provisional 85/58) (not shown). In another arrangement the drum is of frusto-conical form based on a 45 degrees cone and with its axis at 45 degrees to the direction of the beam. Construction of double-image polariser and analyser for ultra-violet light. Two prismatic components of quartz are assembled to constitute a Wollaston prism with a 48 minute separation, the components being separated by a thin film of medicinal paraffin and secured together mechanically outside the optical path.