Roussin's black salt

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Roussin's Black Salt
Structure of Roussin's Black Salt.png
CAS number 12518-87-5
Molecular formula Fe4N7NaO7S3
Molar mass 552.67 g/mol
Appearance Black needles
Melting point 198 to 200 °C (388 to 392 °F; 471 to 473 K)
Related compounds
Related Roussin's Red Salt
Except where noted otherwise, data are given for materials in their standard state (at 25 °C (77 °F), 100 kPa)
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Infobox references

Roussin's black salt is a chemical compound with the formula NaFe4S3(NO)7. It is classified as metal nitrosyl compound. It consists of the sodium salt of the [Fe4S3(NO)7] anion. The cluster anion has the geometry of an incomplete cubane with C3v symmetry.


Roussin’s Black Salt is produced by the reaction of nitrous acid, potassium hydroxide, potassium sulfide, and iron(II) sulfate in aqueous solution.[1] It can also be formed by the conversion of Roussin's Red Salt in mildly acidic conditions. This reaction is reversible and Roussin’s Red Salt is reformed upon alkalization of the reaction solution.


Roussin’s Black Salt is a nitric oxide donor. The nitric oxide donated by Roussin’s Black Salt has proven to be toxic to some melanoma cancer cells.[2] Also, Roussin’s Black Salt demonstrates antibacterial activity in some food processing applications.[3]

See also[edit]



  1. ^ L. Marchlewski; J. Sacks. “Studien über Roussins Salz.” Z. Anorg. Chem. 1892, 2, 175–181.
  2. ^ Janczyk, A.; et al.. "NO-dependent phototoxicity of Roussin’s black salt against cancer cells." Nitric Oxide, 2004, 10, 42-50.
  3. ^ Greenwood, N. N.; & Earnshaw, A. (1997). Chemistry of the Elements (2nd Edn.), Oxford:Butterworth-Heinemann


  • Greenwood, N. N.; & Earnshaw, A. (1997). Chemistry of the Elements (2nd Edn.), Oxford:Butterworth-Heinemann. ISBN 0-7506-3365-4.
  • Roussin, M.L. Ann. Chim. Phys 1858, 3, 285.