Racemic Mixture: If the mixture contains an equal amount of pair of enantiomers of a compound then the mixture is said to be a racemic mixture or racemic compound or racemic modification.
It is optically inactive because it contains an equal amount of enantiomers having equal but opposite optical rotation. Hence the resultant optical rotation is zero ( 0 ).
Resolution of racemic mixture: The process of separation of the racemic mixture is known as the resolution of a racemic mixture.
A racemic mixture is separated by using fractional crystallization or by using chiral reagents.
Meso Compounds: The compound which contains chiral carbon or chiral center but also contains a plane of symmetry is called meso compound.
Meso compound is optically inactive due to the internal compensation of optical activity.