Polarimeters are scientific instruments that are used to measure the rotation of a plane of polarized light because it passes through sample of a compound that exhibits optical activity. Several chemical compounds exist in more than single optically active form. Each isomer or optically active form of a compound will be capable to rotate polarized light plane by an amount of characteristic of that isomer.
Polarimetry is a very sensitive and nondestructive method to measuring optical activity exhibited by some organic and inorganic. The human eye nakedly can’t recognize whether the light is polarized, but the polarization effects can be observed by using polarizing filters.
Polarimeter is used to measures the level to which any substance interacts with the plane-polarized light & whether it rotate the plane-polarized light to the right, to the left, or in no way.
A substance is active optically if it rotates the plane-polarized light to right or to the left. While measuring with polarimeter a compound need be optically active and must have a chiral center (a carbon with 4 different attached groups). Depending on the positioning of these 4 different groups about chiral carbon, a compound may rotate the plane-polarized light to the right or to the left. Compounds that don’t rotate light of any kind lack a chiral center.
The direction and number of degrees of rotation are properly measured using polarimeter to offer the observed rotation. This measured calculation must be revised for the length of cell used & the concentration of solution. Comparing the revised observed rotation to the published values can help in identification of unknown compounds.