Two types of photoelectric polarimeter, one of which is a direct reading polarimeter and the other an automatic polarimeter, have been developed to meet the requirement for rapid and continuous measurement of the optical rotation of optically active solution.
In the direct reading polarimeter, each of two plane-polarized beams passes through either a standard liquid container or a sample container and a rotary analyzer, and finally impinges on a photomultiplier. Each of the two photomultipliers receives a flash of light modulated sinusoidally and generates a.c. signals, which are amplified and fed to the phasemeter. The output of the phasemeter indicates the optical rotational angle of the sample.
The automatic polarimeter has two fixed analyzers and CdS cells. Each output of the cells is connected differentially and fed to a balancing motor which is connected mechanically to the polarizers. At first, the outputs of the two cells are balanced. When the samples are inserted into two optical paths, the motor rotates the polarizers until balance is restored. Each of the rotational angles of the polarizers indicates the optical rotational angle of the sample.
The direct reading polarimeter and automatic polarimeter have an over-all accuracy within about±1% and are handy so that they are suitable for the use in the factory.
