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| Names | |
|---|---|
| IUPAC name Ammonium 2,6-dioxo-5-[(2,4,6-trioxo-5-hexahydropyrimidinylidene)amino]-3H-pyrimidin-4-olate | |
| Other names Purpuric acid ammonium salt | |
| Identifiers | |
3D model (JSmol) | |
| ChemSpider |
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| ECHA InfoCard | 100.019.334 |
| EC Number |
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| Properties | |
| C8H8N6O6 | |
| Molar mass | 284.188 g·mol−1 |
| Density | 1.72 g/cm3 (hydrate of ammonium salt) |
Except where otherwise noted, data are given for materials in theirstandard state (at 25 °C [77 °F], 100 kPa). | |
Murexide (NH4C8H4N5O6, or C8H5N5O6·NH3), also calledammonium purpurate orMX, is theammoniumsalt ofpurpuric acid. It is a purple solid that is soluble in water. The compound was once used as anindicator reagent.[1] Aqueous solutions are yellow at lowpH, reddish-purple in weakly acidic solutions, and blue-purple in alkaline solutions.
Murexide is prepared by treatingalloxantin withammonia to 100 °C, or by treating uramil (5-aminobarbituric acid) withmercury oxide.[2] It may also be prepared by digestingalloxan withalcoholic ammonia.
Justus von Liebig andFriedrich Wöhler in Giessen, Germany, had investigated the purple product, murexide, obtained from snake excrement in the 1830s, but this was not an abundant raw material, and a method of using it as a dyestuff was not established at that time.[3] In the 1850s, French colourists and dye-producers, such as Depoully in Paris, succeeded in making murexide from abundant South American guano and of applying it to natural fibres. It was then widely adopted in Britain, France and Germany.
Murexide is used inanalytical chemistry as acomplexometric indicator for complexometric titrations, most often ofcalcium ions,[4] but also forcopper,nickel,cobalt,thorium andrare-earth metals. It functions as a tridentate ligand.[1]
Its use has been eclipsed by calcium-ion selective electrodes.
This article incorporates text from a publication now in thepublic domain: Chisholm, Hugh, ed. (1911). "Murexide".Encyclopædia Britannica. Vol. 19 (11th ed.). Cambridge University Press. p. 36.
