Racemic mixture: Equi-molecular (50:50) mixture of two optical isomers will not rotate the plane of the polarized light, as their rotatory power is equal in magnitude but opposite in sign/ direction. This is called racemic mixture or dl mixture or ± mixture. When a sample consists of a mixture of enantiomers, the effect of each enantiomer cancels out, molecule for molecule. For example, a 50:50 mixture of two enantiomers or a racemic mixture will not rotate plane polarized light and is optically inactive.
Example: the mixture of d & 1- lactic acid.
d & I – lactic acid are derived from muscle and soured milk respectively.
The racemic mixture can be separated into pure Enantiomers form various methods.