It is well know that the sugar water can rotate the plane of linearly polarized light, so light bends when travelling in sugar water. However, do the liquid state of sugar but not the sugar solution also have this property?


1 Answer 1


Molecules in every state - liquid, solid and gaseous - rotate the plane of linearly polarized light - it doesn't matter, because this rotation arises from inherent asymmetry of molecules, which is causing their optical activity

More to the point, not only water solutions of sugars, but also their crystals, molten sugars and even vapor, rotate the plane of linearly polarized light. If you're asking specifically about sucrose checking this may be problematic as it's decomposing during melting, as you can read in this question and here, but I think it still can be done, under vacuum.

You can also check these related questions about chiral gases and rotation of the plane of polarization by molecules

  • $\begingroup$ This is indeed a helpful answer! Thanks a lot, Mithoron. But a further question come to my head. For those chiral gases, do they have a non-chiral state? I.e., keeping molecules unchanged, if one heats the whole system, will the system in a chaos state that cannot bend light to a certain direction? (By checking the question you refer to, I didn't find the answer for the second question). $\endgroup$
    – user17341
    Commented Jul 8, 2015 at 12:21
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    $\begingroup$ @hongchaniyi No in gas these molecules already point in every direction, the last question I linked is related to that imo. However in more obscure chiral molecules like some of those in this answer chemistry.stackexchange.com/a/31296/9961 highier temperature may cause losing of chirality (racemisation). $\endgroup$
    – Mithoron
    Commented Jul 8, 2015 at 13:09

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