Abstract
The aim of this practical biophysics experiment is to measure the concentration of sucrose solutions using a polarimeter.
Extract
[...] Polarimetry Task: Measure the concentration of the prepared sucrose solutions using a polarimeter. Protocol: Principle of polarimetry: Polarimetry is an experimental technique based on measuring the deviation of the plane of polarization of polarized light passing through a solution composed of one or more optically active molecules such as molecules with an asymmetric carbon atom (i.e. a carbon atom attached to four different groups). The rotation of the plane of polarized light is proportional to the concentration c of the solution, and the path length l. [...]
[...] Open the polarimeter cover and make sure the cuvette compartment is empty. 3. Adjust the equal illumination of both halves of the visual field of the telescope. Its responses to the zero position on the circular scale of the polarimeter. 4. Fill up the cell = 10 cm long) with the sucrose solution without bubbles and put it into the instrument. Observe the visual field with the telescope - both halves are illuminated differently. 5. Rotate the analyzer connected with the scale until both halves of the visual field are equally intensive illuminated. [...]
[...] Calculate the rotation angle as a difference between the actual position and the zero position of the analyzer. 7. Determine the concentration c (in of the studied solution according to formula 8. Calculate the relative error of measurement for each unknown sucrose concentration and determine the average relative error to be compared to the permissible average relative error of measurement (below 9. Rinse the cuvette with distilled water and store everything in its original place. Results: The measurement and calculation results are presented in Table 1 below. [...]
[...] This indicates that the measurements made using the polarimeter show a slight deviation in average. The relative error is particularly high in Solution 1 (20.0 Possible sources of error can be for example: - Temperature variations during the experiment: is given for a temperature of 20°C, - Misreading in the polarimeter, - Incomplete sample preparation or cleaning, - Evaporation of the of the prepared sucrose solutions. The relative error of the concentrations of solutions 2 and 3 show values below the limits of the permissible relative error. [...]
