Sodium bismuthate

Sodium bismuthate is an inorganic compound, and a strong oxidiser.[3] It is somewhat hygroscopic,[2] but not soluble in cold water, 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.[4]

Sodium bismuthate

NaBiO3 powder.
Names
Other names
Sodium bismuth oxide
Identifiers
3D model (JSmol)
ChemSpider
ECHA InfoCard 100.032.220
EC Number
  • 235-455-6235-455-6
UNII
Properties
NaBiO3
Molar mass 279.968 g/mol
Appearance Yellow to yellowish-brown odorless powder[1]
Density 6.50 g/cm3
Insoluble in cold, decomposes in hot water[2]
Hazards
Harmful (Xn)
R-phrases (outdated) R22, R36/37/38
S-phrases (outdated) S26, S36
Lethal dose or concentration (LD, LC):
420 mg/kg (rat, oral)[1]
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
N verify (what is YN ?)
Infobox references

A related compound with the approximate formula Na3BiO4 also exists.[5]

Structure

Sodium bismuthate adopts an ilmenite structure, consisting of octahedral 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.[6]

Synthesis

Bismuth oxidizes to the +V oxidation state 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 + 6NaOH + 2Br2 → 2 NaBiO3 + 4NaBr + 3H2O

Another synthesis of NaBiO3 involves oxidizing a mixture of sodium oxide and bismuth(III) oxide with air (as the source of O2):[7]

Na2O + Bi2O3 + O2 → 2 NaBiO3

The procedure is analogous to the oxidation of manganese dioxide in alkali to give sodium manganate.

Vial of NaBiO3

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]

2 NaBiO3 + H2O → 2 NaOH + Bi2O3 + O2

It is decomposed faster by acids. In HCl, NaBiO3 also reacts to form chlorine gas.[2]

NaBiO3 may be used to detect manganese qualitatively and quantitatively. As a strong oxidizer, it converts almost any manganese compound to permanganate, which is easily assayed spectrophotometrically.[3] To do this, some NaBiO3 and the sample are reacted in a hot solution of sulfuric acid or nitric acid.[2] Permanganate has a violet color and maximum absorbance at 510 nm. The reaction is:

2 Mn2+ + 5 NaBiO3 + 14 H+ → 2 MnO4− + 5 Bi3+ + 5 Na+ + 7 H2O

Sodium bismuthate can perform oxidative 1,2-cleavage on glycols, ketols and alpha hydroxy acids with no further oxidation of the (possible) aldehyde products:[8]

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 at room temperature. Alcohols like methanol or ethanol 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.[8]

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.[1] 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.[9]

References
  • Suzuki, Hitomi (2001). Suzuki, Hitomi; Matano, Yoshihiro (eds.). Organobismuth Chemistry. Elsevier. ISBN 978-0-444-20528-5.

Citations
  1. "Sodium bismuthate". Mallinckrodt Baker. 2007-06-19.
  2. The Merck index (12th ed.). Chapman & Hall Electronic Pub. Division. 2000. p. 1357. ISBN 9781584881292.
  3. Greenwood, Norman N.; Earnshaw, Alan (1997). Chemistry of the Elements (2nd ed.). Butterworth-Heinemann. ISBN 978-0-08-037941-8.
  4. Suzuki, pp. 1-20
  5. Sascha, Vensky (2004). Konformationsaufklärung anorganischer Oxoanionen des Kohlenstoffs und Festkörpersynthesen durch Elektrokristallisation von Ag3O4 und Na3BiO4 (PDF) (Ph.D.) (in German). Max-Planck-Institut für Festkörperforschung, Stuttgart. doi:10.18419/opus-6540.
  6. Kumada, N.; Kinomura, N.; Sleight, A. W. (2000). "Neutron powder diffraction refinement of ilmenite-type bismuth oxides: ABiO3 (A = Na, Ag)". Materials Research Bulletin. 35 (14–15): 2397–2402. doi:10.1016/S0025-5408(00)00453-0. – via ScienceDirect (Subscription may be required or content may be available in libraries.)
  7. Greenwood NN (1997). Chemistry of the elements (2nd ed.). Butterworth-Heinemann. p. 578. ISBN 9780080379418.
  8. Suzuki, p. 373
  9. Dusinska, M; et al. (2013-12-12). "Opinion on bismuth citrate" (PDF). Scientific Committee on Consumer Safety. doi:10.2772/74214. ISBN 9789279301223. SCCS Number: SCCS/1499/12.
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