Sulfanilic acid

From Wikipedia, the free encyclopedia
Jump to navigation Jump to search
Sulfanilic acid
Skeletal formula of sulfanilic acid
Ball-and-stick model of the sulfanilic acid zwittrion
Sample of Sulphanilic acid.jpg
Preferred IUPAC name
4-Aminobenzene-1-sulfonic acid[1]
Other names
4-Aminobenzenesulfonic acid
p-Aminobenzenesulfonic acid
Sulfanilic acid (not retained[1])
3D model (JSmol)
ECHA InfoCard 100.004.075
Molar mass 173.19
Density 1.485
Melting point 288 °C (550 °F; 561 K)
12.51 g/L
Acidity (pKa) 3.25 at 298K
Related compounds
Related sulfonic acids
Benzenesulfonic acid
p-Toluenesulfonic acid
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
☒N verify (what is ☑Y☒N ?)
Infobox references

Sulfanilic acid (4-aminobenzenesulfonic acid) is an off-white crystalline solid which finds application in quantitative analysis of nitrate and nitrite ions. The solid acid exists as a zwitterion, and has an unusually high melting point.[2]


Sulfanilic acid can be produced by sulfonation of aniline:[3]

Synthetic route of sulfanilic acid from aniline.png


As the compound readily forms diazo compounds, it is used to make dyes and sulpha drugs.[2] This property is also used for the quantitative analysis of nitrate and nitrite ions by diazonium coupling reaction with N-(1-Naphthyl)ethylenediamine, resulting in an azo dye, and the concentration of nitrate or nitrite ions were deduced from the color intensity of the resulting red solution by colorimetry.[4]

Diazo coupling of sulfanilic acid and N-1-(Naphthyl)ethylenediamine.png

It is also used as a standard in combustion analysis and in the Pauly reaction.


End uses[edit]

Sulfanilic acid has four primary end uses. It is used as an intermediate in the production of yellow food dye, specific pharmaceutical applications, optical brighteners for white paper and as a concrete additive. The sulfanilic acid intermediate can be purchased in four different grades - technical grade, pure grade, sodium sulfanilate solution and sodium sulfanilate dry powder.

See also[edit]


  1. ^ a b Nomenclature of Organic Chemistry : IUPAC Recommendations and Preferred Names 2013 (Blue Book). Cambridge: The Royal Society of Chemistry. 2014. p. 789. doi:10.1039/9781849733069-FP001. ISBN 978-0-85404-182-4. The name ‘sulfanilic acid’ is not retained.
  2. ^ a b "Sulphanilic acid". A Dictionary of Chemistry. Oxford University Press, 2000. Oxford Reference Online. Oxford University Press.
  3. ^ Siegfried Hauptmann: Organische Chemie, 2nd Edition, VEB Deutscher Verlag für Grundstoffindustrie, Leipzig, 1985, p. 511, ISBN 3-342-00280-8.
  4. ^ G. H. Jerffery; J. Bassett; J. Mendham; R. C. Denney (1989). "Colorimetry and Spectrophotometry". Vogel's Textbook of Quantitative Chemical Analysis, 5th Edition. Longman. p. 702. ISBN 0-582-44693-7.