Acid, pyrotartaric tartaric

Oxalic acid—Malonic acid—Succinic acid—Glutaric acid— Pyrotartaric acid—Itaconic acid—Citraconic acid—Mesa-conic acid—Malic acid—Tartaric acid—Bourgoin s deductions—K kul maleic, brom-maleic and fumaric acids.. 25-31... 

On triturating the calcium tartrate with dilute sulphuric acid, gypsum was precipitated and on evaporating the filtrate to a syrup, crystals, which were tartaric acid, shot on cooling. By adding a solution of barilla (sodium carbonate), acid and neutral sodium tartrates were prepared from the acid. Ammonium tartrate crystals were prepared and distilled, and the formation of pyrotartaric acid and tartaric anhydride seems to have been detected. Cavendish found that a solution of calcium tartrate becomes turbid on heating, indicating a decrease of solubility with rise of temperature. 

Rea.ctlons, When free (R-R, R -tartaric acid (4) is heated above its melting point, amorphous anhydrides are formed which, on boiling with water, regenerate the acid. Further heating causes simultaneous formation of pymvic acid, CH COCOOH pyrotartaric acid, HOOCCH2CH(CH2)COOH and, finally, a black, charred residue. In the presence of a ferrous salt and hydrogen peroxide, dihydroxymaleic acid [526-84-1] (7) is formed. Nitrating the acid yields a dinitro ester which, on hydrolysis, is converted to dihydroxytartaric acid [617 8-1] (8), which upon further oxidation yields tartronic acid [80-69-3] (9). 

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