In this experiment, the user will prepare a sugar solution of known concentration (c), but unknown identity. The user will obtain the observed rotation (αobs) from the experiment using the polarimeter and use that information to calculate the specific rotation [α] of the given sample using the above formula. The identity of the sample can thus be found out from the given list of specific rotations for different chemicals.

The procedure to perform this experiment is self-explanatory and leads the user in a step-by step manner to accomplish the task. The protocol briefly involves the following steps:

User will click on the virtual lab link (simulator).

To know details regarding the instrumentation of the polarimeter.

i. Click on "Know Your Polarimeter" option.
ii. Click on the Polarimeter to Zoom-in as indicated by an arrow.
iii. Click on the red button provided to switch on the polarimeter and to see the light source in the polarimeter instrument.
iv. Click on the panel indicated by arrow to open the sample chamber.
v. After you see 100% Intensity of the light coming through the eye piece at α²⁰_D then click Continue.
vi. Click on the button "click to record experiment without login" to perform an experiment and further follow instructions as detailed in step 3.

To directly perform an experiment using the polarimeter.

i. Click on any of the 6 sugar sample in the bottles on the shelves.
ii. Type in the amount of sugar (in gm/100mL) that you want to use for the experiment in the text box provided and then presses enter on the keyboard.
iii. Click on one of the sample cells to transfer the prepared sugar solution into a cell of particular path length.
iv. After transferring the contents into the sample cell, click on the sample cell to place it into the polarimeter's sample chamber.
v. Click on the power button to switch on the polarimeter to record the optical rotation of the sample.
vi. To rotate the dial of the eye piece in clockwise direction click on '+' button and for anticlockwise direction click on '-' button.
vii. To change the Increment Factor click on the IF* buttons 1, 5 or 10 accordingly.
viii. Rotate the dial both in clockwise and anti-clockwise directions for the whole 360o until you see a maximum light intensity in the right semicircle, matching the left semicircle exactly.
ix. Click on open record form and note down all the 4 different αobs angles where you observed maximum Intensity.

• Estimate the specific rotation [α] using the equation for liquids.
• Compare the obtained specific rotation [α] value against the table provided below to identify the identity of the sugar used in the experiment.
• Click on save form and perform calculations and choose the appropriate identity of the unknown sugar you have used in the experiment.
• Either click on "Click to restart the experiment" and follow the instructions from step 3 or "Click to try with same sample sugar" and follow the instructions from step 3, substep (ii).

*NOTE: While doing the experiments you will notice that if the maximum intensity of light is observed at x° degree, it is also observed at (180+ x)° degree. From a single experiment, it is not possible to infer which the value for total rotation αtotal actually is. Then again, the observation only tells us about the orientation of the plane of polarization of the emergent light relative to that of the incident light. However, one can not off hand say anything about what is the actual total rotation the plane has undergone. Thus, for example, the observation of maxima at x° and at (180 + x)° may mean that the value of αtotal could also be (360n + x) °; where n = 0, 1, 2, … Similarly, it could also be that αtotal is -(360 - x)° or –(360 - (180 + x))° depending on whether the rotation of the light has taken place in the anticlockwise or clockwise direction. For example if the maximum intensity is observed at α value of 30° and 210° , then could be any one of the values: 30°, 210°, -330°, -150° or even 7390° or 570°. To confirm the actual value of αtotal, one needs to repeat the experiment using different concentration and variable path lengths. Though there would be an ambiguity regarding the αtotal for each of these experiments, the correct choices would provide the same specific rotation [α]^T_λ or [α]²⁰_D

Sample data for the experiment