Sodium bismuthate is an inorganic compound, and a strong

oxidiser An oxidizing agent (also known as an oxidant, oxidizer, electron recipient, or electron acceptor) is a substance in a redox chemical reaction that gains or " accepts"/"receives" an electron from a (called the , , or ). In other words, an oxid ...

with chemical formula NaBiO₃. It is somewhat

hygroscopic Hygroscopy is the phenomenon of attracting and holding water molecules via either absorption or adsorption from the surrounding environment, which is usually at normal or room temperature. If water molecules become suspended among the substan ...

, but not soluble in cold

water Water (chemical formula ) is an Inorganic compound, inorganic, transparent, tasteless, odorless, and Color of water, nearly colorless chemical substance, which is the main constituent of Earth's hydrosphere and the fluids of all known living ...

, which can be convenient since the reagent can be easily removed after the reaction. It is one of the few water insoluble sodium salts. Commercial samples may be a mixture of bismuth(V) oxide, sodium carbonate and

sodium peroxide Sodium peroxide is an inorganic compound with the formula Na2O2. This yellowish solid is the product of sodium ignited in excess oxygen. It is a strong base. This metal peroxide exists in several hydrates and peroxyhydrates including Na2O2·2H ...

. A related compound with the approximate formula Na₃BiO₄ also exists.

Structure

Sodium bismuthate adopts an

ilmenite Ilmenite is a titanium-iron oxide mineral with the idealized formula . It is a weakly magnetic black or steel-gray solid. Ilmenite is the most important ore of titanium and the main source of titanium dioxide, which is used in paints, printing ...

structure, consisting of

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 a ...

bismuth(V) centers and sodium cations. The average Bi–O distance is 2.116 Å. The ilmenite structure is related to the corundum structure ( Al₂O₃) with a layer structure formed by close packed oxygen atoms with the two different cations alternating in octahedral sites.

Synthesis

Bismuth oxidizes to the +V

oxidation state In chemistry, the oxidation state, or oxidation number, is the hypothetical charge of an atom if all of its bonds to different atoms were fully ionic. It describes the degree of oxidation (loss of electrons) of an atom in a chemical compound. C ...

only with difficulty in the absence of alkali. Synthesis is performed by making a suspension of bismuth trioxide in a boiling sodium hydroxide solution. It is then oxidized by addition of bromine to form sodium bismuthate. :Bi₂O₃ + 6 NaOH + 2 Br₂ → 2 NaBiO₃ + 4 NaBr + 3 H₂O Another synthesis of NaBiO₃ involves oxidizing a mixture of

sodium oxide Sodium oxide is a chemical compound with the formula Na2 O. It is used in ceramics and glasses. It is a white solid but the compound is rarely encountered. Instead "sodium oxide" is used to describe components of various materials such as glass ...

and

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) ...

with air (as the source of O₂): :Na₂O + Bi₂O₃ + O₂ → 2 NaBiO₃ The procedure is analogous to the oxidation of manganese dioxide in alkali to give

sodium manganate Sodium manganate is the inorganic compound with the formula Na2 Mn O4. This deep green solid is a rarely encountered analogue of the related salt K2MnO4. Sodium manganate is rare because it cannot be readily prepared from the oxidation of mang ...

Reactions

Storage conditions with moisture and high temperatures are detrimental to sodium bismuthate, as it oxidizes water, decomposing into sodium hydroxide and bismuth(III) oxide: :2 NaBiO₃ + H₂O → 2 NaOH + Bi₂O₃ + O₂ It is decomposed faster by acids. In HCl, NaBiO₃ also reacts to form

chlorine gas Chlorine is a chemical element with the Symbol (chemistry), symbol Cl and atomic number 17. The second-lightest of the halogens, it appears between fluorine and bromine in the periodic table and its properties are mostly intermediate betwee ...

. NaBiO₃ may be used to detect manganese qualitatively and quantitatively. As a strong oxidizer, it converts almost any manganese compound to

permanganate A permanganate () is a chemical compound containing the manganate(VII) ion, , the conjugate base of permanganic acid. Because the manganese atom is in the +7 oxidation state, the permanganate(VII) ion is a strong oxidizing agent. The ion is a tr ...

, which is easily assayed spectrophotometrically. To do this, some NaBiO₃ and the sample are reacted in a hot solution of sulfuric acid or nitric acid. Permanganate has a violet color and maximum

absorbance Absorbance is defined as "the logarithm of the ratio of incident to transmitted radiant power through a sample (excluding the effects on cell walls)". Alternatively, for samples which scatter light, absorbance may be defined as "the negative lo ...

at 510 nm. The reaction is: :2 Mn²⁺ + 5 NaBiO₃ + 14 H⁺ → 2 + 5 Bi³⁺ + 5 Na⁺ + 7 H₂O Sodium bismuthate can perform oxidative 1,2-cleavage on

glycol A diol is a chemical compound containing two hydroxyl groups ( groups). An aliphatic diol is also called a glycol. This pairing of functional groups is pervasive, and many subcategories have been identified. The most common industrial diol is e ...

ketol In organic chemistry a hydroxy ketone (often referred to simply as a ketol) is a functional group consisting of a ketone flanked by a hydroxyl group. In the two main classes, the hydroxyl group can be placed in the alpha and beta carbon, alpha posi ...

s and

alpha hydroxy acid α-Hydroxy acids, or alpha hydroxy acids (AHAs), are a class of chemical compounds that consist of a carboxylic acid with a hydroxyl group substituent on the adjacent (alpha) carbon. Prominent examples are glycolic acid, lactic acid, mandelic ac ...

s with no further oxidation of the (possible)

aldehyde In organic chemistry, an aldehyde () is an organic compound containing a functional group with the structure . The functional group itself (without the "R" side chain) can be referred to as an aldehyde but can also be classified as a formyl grou ...

products:Suzuki, p. 373 :R₂C(OH)–C(OH)–R₂ → R₂C=O + O=CR₂ :R₂C(OH)–C(O)–R → R₂C=O + RCOOH :R₂C(OH)–COOH → R₂C=O + CO₂ These cleavages can be done in the presence of acetic or

phosphoric acid Phosphoric acid (orthophosphoric acid, monophosphoric acid or phosphoric(V) acid) is a colorless, odorless phosphorus-containing solid, and inorganic compound with the chemical formula . It is commonly encountered as an 85% aqueous solution, w ...

at room temperature. Alcohols like methanol or

ethanol Ethanol (abbr. EtOH; also called ethyl alcohol, grain alcohol, drinking alcohol, or simply alcohol) is an organic compound. It is an alcohol with the chemical formula . Its formula can be also written as or (an ethyl group linked to a ...

can be used as the reaction media, as they are oxidized slowly with sodium bismuthate. Lead tetraacetate performs similar reactions, but anhydrous conditions, as required in the use of lead tetraacetate, are not necessary for sodium bismuthate. NaBiO₃ can be used for lab-scale plutonium separation (see bismuth phosphate process).

Safety

NaBiO₃ is a mild mechanical irritant. Upon ingestion it is moderately toxic with symptoms akin to lead poisoning: abdominal pain and vomiting. Large doses cause diarrhea and death. Continued absorption of NaBiO₃ into body causes permanent kidney damage. These effects are due to the toxicity of bismuth. Oral absolute lethal dose (LD₁₀₀) of NaBiO₃ is 720 mg/kg for rats, and 510 mg/kg for rabbits.

References

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Citations

{{Bismuth compounds Sodium compounds Bismuth compounds Oxygen compounds