Roussin's black salt is a
chemical compound
A chemical compound is a chemical substance composed of many identical molecules (or molecular entities) containing atoms from more than one chemical element held together by chemical bonds. A molecule consisting of atoms of only one element ...
with the formula KFe
4S
3(NO)
7. It consists of the potassium salt of the
e4S3(NO)7sup>−
anion
An ion () is an atom or molecule with a net electrical charge.
The charge of an electron is considered to be negative by convention and this charge is equal and opposite to the charge of a proton, which is considered to be positive by convent ...
,
metal nitrosyl
Sodium nitroprusside, a medicinally significant metal nitrosyl-pentacyanoferrate (Fe-III) compound, used to treat hypertension.
Metal nitrosyl complexes are complex (chemistry), complexes that contain nitric oxide, NO, bonded to a transition me ...
compound. First described by Zacharie Roussin in 1858, it is one of the first synthetic
iron-sulfur clusters
Iron–sulfur proteins (or iron–sulphur proteins in British spelling) are proteins characterized by the presence of iron–sulfur clusters containing sulfide-linked di-, tri-, and tetrairon centers in variable oxidation states. Iron–sulfur clu ...
along with
the red salt also bearing his name.
Structure
The cluster anion has the geometry of an incomplete
cubane-type cluster
A cubane-type cluster is an arrangement of atoms in a molecular structure that forms a cube. In the idealized case, the eight vertices are symmetry equivalent and the species has Oh symmetry. Such a structure is illustrated by the hydrocarbon cub ...
with
''C''3v symmetry. The dark colour of the complex is attributed to a number of
charge-transfer interactions.
image:Roussins black salt from crystallographic coordinates.tif, left, Structure of the hydrated ammonium salt of
e4S3(NO)7sup>−.
Synthesis
Roussin’s black salt is produced by the chemical reaction, reaction of nitrous acid, potassium hydroxide, potassium sulfide, and iron(II) sulfate in
aqueous solution
An aqueous solution is a solution in which the solvent is water. It is mostly shown in chemical equations by appending (aq) to the relevant chemical formula. For example, a solution of table salt, or sodium chloride (NaCl), in water would be re ...
. It can also be formed by the conversion of Roussin's red salt in mildly
acid
In computer science, ACID ( atomicity, consistency, isolation, durability) is a set of properties of database transactions intended to guarantee data validity despite errors, power failures, and other mishaps. In the context of databases, a sequ ...
ic conditions. This reaction is reversible and Roussin’s red salt is reformed upon
alkalization of the reaction solution.
Uses
Roussin’s black salt is a
nitric oxide
Nitric oxide (nitrogen oxide or nitrogen monoxide) is a colorless gas with the formula . It is one of the principal oxides of nitrogen. Nitric oxide is a free radical: it has an unpaired electron, which is sometimes denoted by a dot in its che ...
donor. Also, Roussin’s Black Salt exhibits antibacterial activity in some
food processing
Food processing is the transformation of agricultural products into food, or of one form of food into other forms. Food processing includes many forms of processing foods, from grinding grain to make raw flour to home cooking to complex industr ...
applications.
See also
*
Roussin's red salt
Roussin's red salt is the inorganic compound with the formula K2 e2S2(NO)4 This metal nitrosyl was first described by Zacharie Roussin in 1858, making it one of the first synthetic iron-sulfur clusters.
Structure and bonding
Roussin's red salt ani ...
References
{{Nitric oxide signaling
Iron complexes
Sulfur compounds
Nitrosyl complexes