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Armstrong's acid
Names
	Preferred IUPAC name Naphthalene-1,5-disulfonic acid
	Other names Armstrong's acid
Identifiers
CAS Number	81-04-9 ;
3D model (JSmol)	Interactive image; Interactive image;
ChEBI	CHEBI:30890 ;
ChemSpider	6414 ;
ECHA InfoCard	100.001.199
PubChem CID	6666;
UNII	E8FPK78470 ;
CompTox Dashboard (EPA)	DTXSID5046982 ;
	InChI InChI=1S/C10H8O6S2/c11-17(12,13)9-5-1-3-7-8(9)4-2-6-10(7)18(14,15)16/h1-6H,(H,11,12,13)(H,14,15,16) Key: XTEGVFVZDVNBPF-UHFFFAOYSA-N ; InChI=1/C10H8O6S2/c11-17(12,13)9-5-1-3-7-8(9)4-2-6-10(7)18(14,15)16/h1-6H,(H,11,12,13)(H,14,15,16) Key: XTEGVFVZDVNBPF-UHFFFAOYAR;
	SMILES O=S(C2=CC=CC1=C(S(=O)(O)=O)C=CC=C12)(O)=O; O=S(=O)(O)c1cccc2c1cccc2S(=O)(=O)O;
Properties
Chemical formula	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). verify (what is ?) Infobox references

Armstrong's 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]

Production and use

It is prepared by disulfonation of naphthalene with oleum:

C₁₀H₈ + 2 SO₃ → C₁₀H₆(SO₃H)₂

Further sulfonation gives The 1,3,5-trisulfonic acid derivative.^[1]

Reactions and uses

Fusion of Armstrong's 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]

References

^ ^a ^b Gerald Booth "Naphthalene Derivatives" in Ullmann's Encyclopedia of Industrial Chemistry, 2005, Wiley-VCH, Weinheim. doi:10.1002/14356007.a17_009.
^ Senning, Alexander (2007). Elsevier's dictionary of chemoetymology. Elsevier. p. 30. ISBN 978-0-444-52239-9.
^ Shigeru Terabe "Electrokinetic chromatography: An interface between electrophoresis and chromatography" TrAC Trends in Analytical Chemistry 1989, Volume 8, pp. 129–134. doi:10.1016/0165-9936(89)85022-8

[Ullmann-1] Gerald Booth "Naphthalene Derivatives" in Ullmann's Encyclopedia of Industrial Chemistry, 2005, Wiley-VCH, Weinheim. doi:10.1002/14356007.a17_009.

[2] Senning, Alexander (2007). Elsevier's dictionary of chemoetymology. Elsevier. p. 30. ISBN 978-0-444-52239-9.

[3] Shigeru Terabe "Electrokinetic chromatography: An interface between electrophoresis and chromatography" TrAC Trends in Analytical Chemistry 1989, Volume 8, pp. 129–134. doi:10.1016/0165-9936(89)85022-8

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