Sodium bismuthate is an inorganic compound, and a strong oxidiser with chemical formula NaBiO3.[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]
A related compound with the approximate formula Na3BiO4 also exists.[5]
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]
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.[7]
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 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:[citation needed]
These cleavages can be done in the presence of aceticorphosphoric acid at room temperature. Alcohols like methanolorethanol 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.[9]
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.[10]
^Kumada N, Kinomura N, Sleight AW (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.)
^hrsg. von Georg Brauer. Unter Mitarb. von M. Baudler (1975). Handbuch der präparativen anorganischen Chemie / 1 (in German). Stuttgart: Enke. p. 604. ISBN3-432-02328-6. OCLC310719485.
^Greenwood NN (1997). Chemistry of the elements (2nd ed.). Butterworth-Heinemann. p. 578. ISBN9780080379418.
