What will affect the polarimeter?

What factors affect the polarimeter

(1) Solvent

The optical rotation of an optically active substance depends mainly on the structure of the substance itself. In addition, it is related to the thickness of the light-transmitting substance, the wavelength and temperature of the light used in the measurement. If the substance to be tested is a solution, the influencing factors include the concentration of the substance, and the solvent also has a certain influence. Therefore, the optical rotation of the optically active substance is usually different under different conditions.

(2) Temperature

An increase in temperature causes the optical tube to expand and lengthen, resulting in a decrease in the density of the liquid to be tested. In addition, the temperature change will cause association or dissociation between molecules of the substance to be tested, and the optical rotation will change. Different materials have different temperature coefficients, generally between -(0.01~0.04) Â°C. For this purpose, it must be thermostated during the experimental measurement, and the thermostat jacket is equipped with a thermostatic jacket and connected to the super constant temperature bath.

(3) Concentration and length of optical tube

Under certain experimental conditions, the optical rotation of the optically active substance is often considered to be proportional to the concentration, because the specific optical rotation is regarded as a constant. The optical rotation and the solution concentration are 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 tube. The optical tube usually has three specifications of 10 cm, 20 cm, and 22 cm. Often used are 10cm in length. However, for solutions with weaker or weaker optical rotation, in order to improve the accuracy and reduce the relative error of the reading, a 20 cm or 22 cm length of optical tube is required.