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| Polari meter 220 mm
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| An ideal instrument for quality control with better accuracy. Suitable for testing sugar solution and other optically active liquids. Accommodate 220 mm. length tube. The polarimeter consists basically of two polarizing elements of 'Polaroid' one of which is fixed, the other capable of rotation and mounted within a graduated scale in order to measure its orientation with respect to the other. When the planes of polarisation of the two elements are mutually perpendicular no light is transmitted through the system. A thin plate of quartz is positioned to cover half the aperture of one of the elements in order to introduce a 'half shadow effect'. The effects to cause an extinction of light in one half of the field a few degrees normally 7 degrees, before the other half of the field reaches its extinction position. Thus a balance can be achieved where one half of the field is reducing in intensity as the other half is increasing, as the scale is rotated. The position of the scale at which the two halves are of equal intensity is the balance position and is used in all determinations. On introducing an optically active sample between the polarizing elements the balance is disturbed and it is necessary to rebalance by turning the scale. The amount by which the scale is moved a direct measure of the sample optical activity. |
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