What are the factors that cause deviations in polarimeter test results?

What are the factors that cause deviations in polarimeter test results? (1) Influence of solvent The optical rotation of optically active substances mainly depends on the structure of the substance itself
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In addition, it is also related to the thickness of the light passing through the material, the wavelength and temperature of the light used in the measurement
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If the measured substance is a solution, the influencing factors also include the concentration of the substance, and the solvent also has an influence
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Therefore, the optical rotation of optically active substances is usually different under different conditions
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(2) The influence of temperature The increase of temperature will make the optical rotation tube expand and lengthen, which will reduce the density of the liquid to be measured
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In addition, the temperature change will also cause the association or dissociation between the molecules of the substance to be tested, which will change the optical rotation
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Different substances have different temperature coefficients, generally between -(0.
01 ~ 0.
04) °C
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For this reason, the constant temperature is maintained during the experimental measurement, and a constant temperature jacket is installed on the optical rotation tube, which is connected to the constant temperature tank
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(3) Effect of concentration and optical rotation tube length on the relative optical rotation Under experimental conditions, the optical rotation of the optically active substance is often regarded as proportional to the concentration, because the specific optical rotation is regarded as a constant
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However, the relationship between optical rotation and solution concentration is not strictly linear, so strictly speaking, the specific optical rotation is not constant, and the optical rotation is proportional to the length of the optical rotation tube
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Polarimeter tubes usually have three sizes of 10cm, 20cm and 22cm
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There are 10cm lengths that are often used
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However, for solutions with weak or dilute optical rotation ability, in order to improve the accuracy and reduce the relative error of readings, a 20cm or 22cm length of optical rotation tube is required.

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 　　The above is the relevant introduction about the reasons for the deviation of the polarimeter test results.
I believe that everyone has a corresponding understanding of this after reading, and everyone can use it as a reference.
I hope it can help everyone
.