|Molar mass||342.16 g/mol|
|Density||1.68 g/cm3, 2.078 (calc.)|
|Melting point||> 300 °C (572 °F; 573 K)|
|Boiling point||678 °C (1,252 °F; 951 K) (calc.)|
|Acidity (pKa)||1.40, 2.19, 3.31, 4.78, 5.89, 6.96|
Except where noted otherwise, data is given for materials in their standard state (at 25 °C (77 °F), 100 kPa)
|what is: / ?)(|
Mellitic acid, also called graphitic acid or benzenehexacarboxylic acid, is an acid first discovered in 1799 by M. H. Klaproth in the mineral mellite (honeystone), which is the aluminium salt of the acid.
Mellitic acid may be prepared by warming mellite with ammonium carbonate, boiling off the excess of the ammonium salt, and adding ammonia to the solution. The precipitated alumina is filtered off, the filtrate evaporated, and the ammonium salt of the acid purified by recrystallization. The ammonium salt is then converted into the lead salt by precipitation with lead acetate, and the lead salt is then decomposed by hydrogen sulfide. The acid may also be prepared by the oxidation of pure carbon or hexamethyl benzene, by alkaline potassium permanganate in the cold, or by hot concentrated nitric acid.
Mellitic acid crystallizes in fine silky needles and is soluble in water and alcohol. It is a very stable compound; chlorine, concentrated nitric acid and hydriodic acid do not react with it. It is decomposed, on dry distillation, into carbon dioxide and pyromellitic acid, C10H6O8; when distilled with lime it gives carbon dioxide and benzene. Long digestion of the acid with an excess of phosphorus pentachloride forms the acid chloride, which crystallizes in needles, and melts at 190 °C. By heating the ammonium salt of the acid to 150–160 °C while ammonia is evolved, a mixture of paramide (mellimide, molecular formula C
3), and ammonium euchroate is obtained. The mixture may be separated by dissolving out the ammonium euchroate with water. Paramide is a white amorphous powder, insoluble in water and alcohol.
The high stability of mellitic acid salts and their presence as an endproduct of the oxidation of polycyclic aromatic hydrocarbons, which are present in the solar system, make them a possible organic substance in Martian soil.
- MSDS for mellitic acid
- Curate Data: Predicted Properties: 2244. ChemSpider.com.
- Brown, H.C., et al., in Baude, E.A. and Nachod, F.C., Determination of Organic Structures by Physical Methods, Academic Press, New York, 1955.
- Beiträge zur chemischen Kenntniss der Mineralkörper, Band 3 (in German). p. 114.
- S. A. Benner, K. G. Devine, L. N. Matveeva, D. H. Powell (2000). "The missing organic molecules on Mars". Proceedings of the National Academy of Sciences 97 (6): 2425–2430. doi:10.1073/pnas.040539497. PMC 15945. PMID 10706606.
- Kurmoo M, Estournes C, Oka Y, Kumagai H, Inoue K (2005) Inorganic Chemistry volume 44, page 217
Henry Enfield Roscoe, Carl Scholemmer, "Mellitene Group", "A Treatise on Chemistry: V.III: The Chemistry of the Hydrocarbons and their Derivatives on Organic Chemistry: P.V:529. D. Appleton and Co. (1889).