Bismuth oxynitrate is the name applied to a number of compounds that contain Bi³⁺,

nitrate Nitrate is a polyatomic ion with the chemical formula . Salts containing this ion are called nitrates. Nitrates are common components of fertilizers and explosives. Almost all inorganic nitrates are soluble in water. An example of an insolubl ...

ions and

oxide An oxide () is a chemical compound that contains at least one oxygen atom and one other element in its chemical formula. "Oxide" itself is the dianion of oxygen, an O2– (molecular) ion. with oxygen in the oxidation state of −2. Most of the ...

ions and which can be considered as compounds formed from Bi₂O₃, N₂O₅ and H₂O. Other names for bismuth oxynitrate include bismuth subnitrate and bismuthyl nitrate. In older texts bismuth oxynitrate is often simply described as BiONO₃ or basic bismuth nitrate. Bismuth oxynitrate was once called magisterium bismuti or bismutum subnitricum, and was used as a white

pigment A pigment is a colored material that is completely or nearly insoluble in water. In contrast, dyes are typically soluble, at least at some stage in their use. Generally dyes are often organic compounds whereas pigments are often inorganic compou ...

, in beauty care, and as a gentle

disinfectant A disinfectant is a chemical substance or compound used to inactivate or destroy microorganisms on inert surfaces. Disinfection does not necessarily kill all microorganisms, especially resistant bacterial spores; it is less effective than st ...

for internal and external use. It is also used to form Dragendorff's reagent, which is used as a TLC stain. Bismuth oxynitrate is commercially available as Bi₅O(OH)₉(NO₃)₄ (CAS number: ) or as BiONO₃·H₂O (CAS Number: ). Some compounds have been fully characterised with single crystal studies and found to contain the

octahedral In geometry, an octahedron (plural: octahedra, octahedrons) is a polyhedron with eight faces. The term is most commonly used to refer to the regular octahedron, a Platonic solid composed of eight equilateral triangles, four of which meet at ea ...

i₆O_''x''(OH)_8−''x''sup>(10−''x'')+ cation. There is indirect evidence that either the octahedral cation or the octahedral cation is present in aqueous solution following the

polymerisation In polymer chemistry, polymerization (American English), or polymerisation (British English), is a process of reacting monomer molecules together in a chemical reaction to form polymer chains or three-dimensional networks. There are many for ...

of , the Bi³⁺ ion present in acidic solutions. The ion is found in the

perchlorate A perchlorate is a chemical compound containing the perchlorate ion, . The majority of perchlorates are commercially produced salts. They are mainly used as oxidizers for pyrotechnic devices and to control static electricity in food packaging. Per ...

compound Bi₆O₄(OH)₄ClO₄·7H₂O and is

isoelectronic Isoelectronicity is a phenomenon observed when two or more molecules have the same structure (positions and connectivities among atoms) and the same electronic configurations, but differ by what specific elements are at certain locations in the ...

with the octahedral Sn₆O₄(OH)₄ cluster found in the hydrate of

tin(II) oxide Tin(II) oxide (stannous oxide) is a compound with the formula SnO. It is composed of tin and oxygen where tin has the oxidation state of +2. There are two forms, a stable blue-black form and a metastable red form. Preparation and reactions Blue ...

, 3SnO·H₂O. The compounds that contain this are: :Bi₆O₄(HO)₄(NO₃)₆·H₂O (equivalent to BiONO₃·H₂O; Bi₂O₃·N₂O₅·H₂O ) :Bi₆O₄(OH)₄(NO₃)₆·4H₂O (equivalent to BiONO₃·H₂O; Bi₂O₃·N₂O₅·6H₂O ) : i₆O₄(OH)₄Bi₆O₅(OH)₃](NO₃)₁₁, which contains two different cations, i₆O₄(OH)₄sup>6+ and i₆O₅(OH)₃sup>5+ The compound Bi₆O₅(OH)₃(NO₃)₅·3H₂O (equivalent to 6Bi₂O₃·5N₂O₅·9H₂O) also contains the octahedral units but this time they are joined to form ₂. Additionally some oxynitrates have layer structures (a common motif also found in bismuth(III) oxyhalides): :Bi₂O₂(OH)NO₃ (equivalent to BiONO₃·H₂O) contains " i₂O₂sup>2+" layers :Bi₅O₇NO₃, which is

isostructural Isostructural chemical compounds have similar chemical structures. " Isomorphous" when used in the relation to crystal structures is not synonymous: in addition to the same atomic connectivity that characterises isostructural compounds, isomorphous ...

with β-Bi₅O₇I

Cluster cation structure

The octahedral ion has 6 Bi³⁺ ions at the corners of an

octahedron In geometry, an octahedron (plural: octahedra, octahedrons) is a polyhedron with eight faces. The term is most commonly used to refer to the regular octahedron, a Platonic solid composed of eight equilateral triangles, four of which meet at ea ...

. There is no covalent bond between the Bi atoms, they are held in position by bridging O²⁻ and OH⁻ anions, one at the centre of each of the eight triangular faces, bridging three Bi ions. The Bi ions are essentially four coordinate and are at the apex of a flat square pyramid. An ''ab initio'' theoretical study of the hydration mechanism of Bi³⁺ and the structure concludes that the

lone pair In chemistry, a lone pair refers to a pair of valence electrons that are not shared with another atom in a covalent bondIUPAC ''Gold Book'' definition''lone (electron) pair''/ref> and is sometimes called an unshared pair or non-bonding pair. Lone ...

s on the Bi³⁺ ions are stereochemically active.

Preparation

Bismuth oxynitrates can be prepared from bismuth(III) nitrate. For example, hydrolysis of a solution of bismuth nitrate through the addition of alkali or the reaction of the pentahydrate, BiNO₃·5H₂O with KOH, or the controlled

thermal decomposition Thermal decomposition, or thermolysis, is a chemical decomposition caused by heat. The decomposition temperature of a substance is the temperature at which the substance chemically decomposes. The reaction is usually endothermic as heat is req ...

of the pentahydrate. The thermal decomposition of bismuth nitrate pentahydrate proceeds through the following stages: :At pH below 1.0, Bi₆O₄(OH)₄(NO₃)₆·4H₂O (equivalent to BiNO₃·H₂O) is the first solid product, which when heated produces Bi₆H₂O(NO₃)O₄(OH)₄ (equivalent to BiNO₃.H₂O). :Between pH 1.2 and 1.8, further

hydrolysis Hydrolysis (; ) is any chemical reaction in which a molecule of water breaks one or more chemical bonds. The term is used broadly for substitution, elimination, and solvation reactions in which water is the nucleophile. Biological hydrolysis i ...

occurs and Bi₆O₅(OH)₃(NO₃)₅·3H₂O is formed. The final oxynitrate product of thermal dehydration is believed to be Bi₅O₇NO₃, which is isostructural with β–Bi₅O₇I and has a layer structure. The ultimate stage of thermal decomposition of oxynitrates is

bismuth(III) oxide Bismuth(III) oxide is perhaps the most industrially important compound of bismuth. It is also a common starting point for bismuth chemistry. It is found naturally as the mineral bismite (monoclinic) and sphaerobismoite (tetragonal, much more rare) ...

, Bi₂O₃.

References

{{nitrates Bismuth compounds