| Names | |||
|---|---|---|---|
| Preferred IUPAC name Naphthalene-1,5-disulfonic acid | |||
| Other names Armstrong's acid | |||
| Identifiers | |||
3D model (JSmol) | |||
| ChEBI | |||
| ChemSpider | |||
| ECHA InfoCard | 100.001.199 | ||
PubChem CID | |||
| UNII | |||
CompTox Dashboard (EPA) | |||
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| Properties | |||
| C10H8S2O6 | |||
| Molar mass | 288.299 g/mol | ||
| Appearance | colorless solid | ||
| Hazards | |||
| Occupational safety and health (OHS/OSH): | |||
Main hazards | corrosive | ||
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). | |||
Armstrong acid (naphthalene-1,5-disulfonic acid) is a fluorescent organic compound with the formula C10H6(SO3H)2. It is one of several isomers of naphthalenedisulfonic acid. It a colorless solid, typically obtained as the tetrahydrate. [1] Like other sulfonic acids, it is a strong acid. It is named for British chemist Henry Edward Armstrong. [2]
It is prepared by disulfonation of naphthalene with oleum:
Further sulfonation gives The 1,3,5-trisulfonic acid derivative. [1]
Fusion of Armstrong acid in NaOH gives the disodium salt of 1,5-dihydroxynaphthalene, which can be acidified to give the diol. The intermediate in this hydrolysis, 1-hydroxynaphthalene-5-sulfonic acid, is also useful. Nitration gives nitrodisulfonic acids, which are precursors to amino derivatives.
The disodium salt is sometimes used as a divalent counterion for forming salts of basic drug compounds, as an alternative to the related mesylate or tosylate salts. When used in this way such a salt is called a naphthalenedisulfonate salt, as seen with the most common salt form of the stimulant drug CFT. The disodium salt is also used as an electrolyte in certain kinds of chromatography. [3]