What is "racemic acid"

n. (context organic compound English) an equal mixture of the d- and l- forms of tartaric acid found in grape juice; the isomers can be separated via crystallization

n. the optically inactive form of tartaric acid that is often found in grape juice

Racemic acid is an old name for an optically inactive or racemic form of tartaric acid. It is an equal mixture of two mirror-image isomers ( enantiomers), optically active in opposing directions.

Its sodium-ammonium salt is unusual among racemic mixtures in that during crystallization it can separate out into two kinds of crystals, each composed of one isomer, and whose macroscopic shapes are mirror images of each other. Thus, Louis Pasteur was able to separate the two enantiomers by picking apart the crystals.

In a modern-time re-enactment of the Pasteur experiment, it was established that the preparation of crystals was not very reproducible. The crystals deformed, but they were large enough to inspect with the naked eye (microscope not required).