Sodium cobaltinitrite

Sodium cobaltinitrite is inorganic compound with the formula Na₃Co(NO₂)₆. The anion of this yellow-coloured salt consists of the coordination complex [Co(NO₂)₆]^3-. It was a reagent for the qualitative test for potassium and ammonium ions.[1]

Sodium cobaltinitrite

Names
IUPAC name sodium hexanitrocobaltate(III)
Identifiers
CAS Number	13600-98-1
3D model (JSmol)	Interactive image
ChemSpider	13198283
ECHA InfoCard	100.033.692
PubChem CID	16211641
UNII	XO0NGY9EY7
CompTox Dashboard (EPA)	DTXSID00894906
InChI InChI=1S/Co.6NO2.3Na/c;6*2-1-3;;;/q-3;;;;;;;3*+1 Key: IMBXIBFCGMYSME-UHFFFAOYSA-N InChI=1/Co.6NO2.3Na/c;6*2-1-3;;;/q-3;;;;;;;3*+1/rCoN6O12.3Na/c8-2(9)1(3(10)11,4(12)13,5(14)15,6(16)17)7(18)19;;;/q-3;3*+1 Key: IMBXIBFCGMYSME-PEVTYUNUAJ
SMILES [Na+].[Na+].[Na+].O=[N+]([O-])[Co-3]([N+]([O-])=O)([N+](=O)[O-])([N+]([O-])=O)([N+]([O-])=O)[N+]([O-])=O
Properties
Chemical formula	CoN6Na3O12
Molar mass	403.933 g·mol^−1
Density	2.565 g/cm^3
Hazards
Safety data sheet	JT Baker MSDS
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Infobox references

Synthesis and reactions

The compound is prepared by oxidation of cobalt(II) salts in the presence of sodium nitrite:[2]

4 [Co(H₂O)₆](NO₃)₂ + O₂ + 24 NaNO₂ → 4 Na₃[Co(NO₂)₆] + 8 NaNO₃ + 4 NaOH + 22 H₂O

Application for analysis of potassium

Although the sodium cobaltinitrite is soluble in water, it forms the basis of a quantitative determination of potassium, thallium, and ammonium ions. Under the recommended reaction conditions the insoluble double salt, K₂Na[Co(NO₂)₆]·H₂O is precipitated and weighed.[3] In geochemical analysis, sodium cobaltinitrite is used to distinguish alkali feldspars from plagioclase feldspars in thin section.[4]

• 
  Concentrated aqueous solution of sodium cobaltinitrite.
• 
  K₂Na[Co(NO₂)₆]·H₂O.

Fragment of the Na₃Co(NO₂)₆ lattice, highlighting the CoN₆ and NaO₆ coordination spheres.[5]

See also

• Potassium cobaltinitrite

References

1. Greenwood, Norman N.; Earnshaw, Alan (1997). Chemistry of the Elements (2nd ed.). Butterworth-Heinemann. ISBN 978-0-08-037941-8.
2. Glemser, O. (1963). "Sodium Hexanitritocobaltate(III)". In Brauer, G. (ed.). Handbook of Preparative Inorganic Chemistry. 1 (2nd ed.). New York, NY: Academic Press. p. 1541.
3. Vogel, A. I. (1951). Quantitative Inorganic Analysis (2nd ed.). Longmans Green and Co.
4. Bailey, E. H.; Stevens, R. E. (1960). "Selective staining of K-feldspar and plagioclase on rock slabs and thin sections". American Mineralogist. 45: 1020–1025.
5. Brian N. Figgis, Alexandre N. Soboleva (2001). "Na₃Co(NO₂)₆ at 293 and 10 K". Acta Crystallographica Section C. 57 (Pt 8): 885–886. doi:10.1107/S0108270101007995. PMID 11498599.CS1 maint: uses authors parameter (link)