posted by Jason .
An optical rotation study gives a result of alpha=+140 degrees. Suggest a dilution experiment to test whether the result is indeed +140 degrees, and not -220 degrees.
-could polarimetry experiment be used to find the r and s isomer?
Yes, I think it can. This problem has been posted before and I suggested diluting the sample by a factor of 10 and measuring the rotation. If the original was indeed 140 degrees, then the new measurement would show 14.0 degrees. If the original measurement was -220 degrees, the new measurement would be -22.0 degrees. There would be no confusion between +14 and -22. Check my thinking.