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Racemic acid is an old name for an optically inactive or
"Sur les relations qui peuvent exister entre la forme cristalline, la composition chimique et le sens de la polarisation rotatoire"
while he presented his resolution of racemic acid into separate
"Recherches sur les propriétés spécifiques des deux acides qui composent l'acide racémique"
In the latter paper, Pasteur sketches from natural concrete reality chiral polytopes quite possibly for the first time. The optical property of tartaric acid was first observed in 1832 by Jean Baptiste Biot, who observed its ability to rotate polarized light. It remains unknown whether Arthur Cayley or
Racemic acid is an old name for an optically inactive or racemic
In chemistry, a racemic mixture, or racemate (), is one that has equal amounts of left- and right-handed enantiomers of a chiral molecule or salt. Racemic mixtures are rare in nature, but many compounds are produced industrially as racemates. ...
form of tartaric acid
Tartaric acid is a white, crystalline organic acid that occurs naturally in many fruits, most notably in grapes, but also in bananas, tamarinds, and citrus. Its salt, potassium bitartrate, commonly known as cream of tartar, develops naturally ...
. It is an equal mixture of two mirror-image isomers
In chemistry, isomers are molecules or polyatomic ions with identical molecular formulae – that is, same number of atoms of each element – but distinct arrangements of atoms in space. Isomerism is existence or possibility of isomers.
...
( enantiomers), optically active in opposing directions. It occurs naturally in grape juice.
Tartaric acid's sodium-ammonium salt
Salt is a mineral composed primarily of sodium chloride (NaCl), a chemical compound belonging to the larger class of salts; salt in the form of a natural crystalline mineral is known as rock salt or halite. Salt is present in vast quant ...
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 crystalline shapes are mirror images of each other. Thus, Louis Pasteur was able in 1848 to isolate each of the two enantiomers by laboriously separating the two kinds crystals using delicate tweezers and a hand lens. Pasteur announced his intention to resolve racemic acid in:
* Pasteur, Louis (1848"Sur les relations qui peuvent exister entre la forme cristalline, la composition chimique et le sens de la polarisation rotatoire"
while he presented his resolution of racemic acid into separate
optical
Optics is the branch of physics that studies the behaviour and properties of light, including its interactions with matter and the construction of instruments that use or detect it. Optics usually describes the behaviour of visible, ultravio ...
isomers in:
* Pasteur, Louis (1850"Recherches sur les propriétés spécifiques des deux acides qui composent l'acide racémique"
In the latter paper, Pasteur sketches from natural concrete reality chiral polytopes quite possibly for the first time. The optical property of tartaric acid was first observed in 1832 by Jean Baptiste Biot, who observed its ability to rotate polarized light. It remains unknown whether Arthur Cayley or
Ludwig Schläfli
Ludwig Schläfli (15 January 1814 – 20 March 1895) was a Swiss mathematician, specialising in geometry and complex analysis (at the time called function theory) who was one of the key figures in developing the notion of higher-dimensional space ...
, or other contemporary mathematicians who studied polytopes, knew of the French work.
In two modern-day re-enactments performed in Japan 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).
See also
*Tartaric acid
Tartaric acid is a white, crystalline organic acid that occurs naturally in many fruits, most notably in grapes, but also in bananas, tamarinds, and citrus. Its salt, potassium bitartrate, commonly known as cream of tartar, develops naturally ...
* Uvitic acid
* Uvitonic acid
References
{{reflist Carboxylic acids Stereochemistry Chirality Polytopes Optical materials Racemic mixtures Food antioxidants Alpha hydroxy acids Dicarboxylic acids Vicinal diols