FTP, name these mixtures of equal parts of enantiomers that do not rotate the plane of incident polarized light.
The treatment of these substances with a naturally occurring base, such as cinchonine, can result in resolution, which is the process by which they are separated into two equal parts.  An ideal example of them is their namesake, also known as tartaric acid, which can be divided into dextro- and leveorotatory components.  For every molecule that light encounters, there is a second molecule, which cancels the effects of the first, rendering them optically inactive.  FTP, name these mixtures of equal parts of enantiomers that do not rotate the plane of incident polarized light.
The treatment of these substances with a naturally occurring base, such as cinchonine, can result in resolution, which is the process by which they are separated into two equal parts.  
racemic mixtures or racemates