Roussin's black salt

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Roussin's Black Salt
Other names
potassium heptanitrosyltri-μ3-thiotetraferrate
3D model (JSmol)
Molar mass 568.70 g·mol−1
Appearance Black solid
Melting point 198 to 200 °C (388 to 392 °F; 471 to 473 K)
Related compounds
Roussin's Red Salt
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
Infobox references

Roussin's black salt is a chemical compound with the formula KFe4S3(NO)7.[1] It consists of the potassium salt of the [Fe4S3(NO)7] anion, metal nitrosyl compound. First described by Zacharie Roussin in 1858,[2] it is the first synthetic iron-sulfur cluster.


The cluster anion has the geometry of an incomplete cubane-type cluster with C3v symmetry. The dark colour of the complex is attributed to a number of charge-transfer interactions.[3]

Structure of the hydrated ammonium salt of [Fe4S3(NO)7].


Roussin’s Black Salt is produced by the reaction of nitrous acid, potassium hydroxide, potassium sulfide, and iron(II) sulfate in aqueous solution.[4] 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.[5] Also, Roussin’s Black Salt exhibits antibacterial activity in some food processing applications.[6]

See also[edit]


  1. ^ Greenwood, Norman N.; Earnshaw, Alan (1997). Chemistry of the Elements (2nd ed.). Butterworth-Heinemann. p. 1094. ISBN 978-0-08-037941-8.
  2. ^ Butler, Anthony R. (July 1982). "The chemist Z. Roussin (1827-94)". Journal of Chemical Education. 59 (7): 549. doi:10.1021/ed059p549.
  3. ^ Jaworska, Maria; Stasicka, Zofia (March 2006). "Structure and UV–vis spectroscopy of roussin black salt [Fe4S3(NO)7]−". Journal of Molecular Structure. 785 (1–3): 68–75. doi:10.1016/j.molstruc.2005.09.030.
  4. ^ Marchlewski, L.; Sachs, J. (1892). "Studien über ROUSINS Salz". Zeitschrift für anorganische Chemie. 2 (1): 175–181. doi:10.1002/zaac.18920020117.
  5. ^ Janczyk, Agnieszka; Wolnicka-Glubisz, Agnieszka; Chmura, Antonina; Elas, Martyna; Matuszak, Zenon; Stochel, Grazyna; Urbanska, Krystyna (February 2004). "NO-dependent phototoxicity of Roussin's black salt against cancer cells". Nitric Oxide. 10 (1): 42–50. doi:10.1016/j.niox.2004.01.009.
  6. ^ Greenwood, Norman N.; Earnshaw, Alan (1997). Chemistry of the Elements (2nd ed.). Butterworth-Heinemann. pp. 1094–1095. ISBN 978-0-08-037941-8.