# Metanilic acid

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Metanilic acid Names Preferred IUPAC name 3-Aminobenzene-1-sulfonic acid Other names 3-Aminobenzenesulfonic acid m-Anilinesulfonic acid Identifiers CAS Number 121-47-1 3D model (JSmol) Interactive image ChemSpider 8161 ECHA InfoCard 100.004.067 EC Number 204-473-6204-473-6 PubChem CID 8474 UNII OT03NUM20P Y UN number 2585 CompTox Dashboard (EPA) DTXSID6024462 InChI InChI=1S/C6H7NO3S/c7-5-2-1-3-6(4-5)11(8,9)10/h1-4H,7H2,(H,8,9,10) SMILES Nc1cccc(S(=O)(=O)O)c1 Properties Chemical formula C6H7NO3S Molar mass 173.19 g·mol−1 Appearance Beige powder Density 1.69 Melting point >300 °C (lit.) Solubility in water Less than 1 mg/mL at 22 °C (72 °F) Acidity (pKa) 3.74 (H2O)[1] Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). Infobox references

Chemical compound

**Metanilic acid** is an [isomer](/source/Isomer) of [sulfanilic acid](/source/Sulfanilic_acid) with molecular formula C 6H 7NO 3S and [molecular weight](/source/Molecular_weight) 173.18968 g/mol.[2][3][4] It is a white powder that is slightly soluble in water.

## Disappearing polymorph

The crystal structure called Form I is a [disappearing polymorph](/source/Disappearing_polymorph) that cannot be produced by researchers anymore while Form II and III still exist.[5] The reason for this is that Form I is converted to another polymorph upon contact with a [seed crystal](/source/Seed_crystal) and most places are contaminated with tiny amounts of Form II or III that are enough to prevent any viable amounts of Form I to be produced.

## See also

- [Orthanilic acid](/source/Orthanilic_acid)

- [Sulfanilic acid](/source/Sulfanilic_acid)

## References

1. **[^](#cite_ref-CRC97_1-0)** Haynes, William M., ed. (2016). [*CRC Handbook of Chemistry and Physics*](/source/CRC_Handbook_of_Chemistry_and_Physics) (97th ed.). [CRC Press](/source/CRC_Press). pp. 5–88. [ISBN](/source/ISBN_(identifier)) [978-1498754286](https://en.wikipedia.org/wiki/Special:BookSources/978-1498754286).

1. **[^](#cite_ref-2)** Pubchem. ["3-AMINOBENZENESULFONIC ACID - C6H7NO3S - PubChem"](https://pubchem.ncbi.nlm.nih.gov/compound/Metanilic_acid). NIH.

1. **[^](#cite_ref-3)** ["Metanilic acid - 121-47-1"](http://chemicalbook.com/ChemicalProductProperty_EN_CB7143612.htm).

1. **[^](#cite_ref-4)** ["Metanilic acid"](http://webbook.nist.gov/cgi/cbook.cgi?ID=121-47-1).

1. **[^](#cite_ref-5)** Rubin-Preminger JM, Bernstein J (2005-07-01). "3-Aminobenzenesulfonic Acid: A Disappearing Polymorph". *Crystal Growth & Design*. **5** (4): 1343–1349. [doi](/source/Doi_(identifier)):[10.1021/cg049680y](https://doi.org/10.1021%2Fcg049680y). [ISSN](/source/ISSN_(identifier)) [1528-7483](https://search.worldcat.org/issn/1528-7483).

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