Shiro Akabori

[44] Preparation and analysis of dihydroxymaleate and hydroxypyruvate

Publisher Summary Dihydroxymaleic acid can be prepared by oxidation of tartaric acid by which crystalline dihydroxymaleic acid hydrate is collected. If recrystallization is necessary, 20 g. of the product is dissolved in 160 ml. of absolute alcohol at room temperature and the solution is filtered. The filtrate is cooled in an ice bath and gently stirred during the dropwise addition of 150 ml. of water; the crystalline dihydroxymaleie acid is collected; washed, and dried. The quantitative determination of dihydroxymaleic acid is based on the reduction property of it, in the presence of salts. The titrimetric method for the quantitative estimation of dihydroxymaleic acid consists in decomposing dihydroxymaleic acid by boiling the aqueous solution and determining the decrease in acidity by titration to phenolphthalein. The use of 2,6-dichlorophenolindophenol to determine dihydroxy- maleic acid is based on the fact that the colored indicator is quantitatively and rapidly reduced by dihydroxymaleic acid in acid solution to a colorless compound.