Lithium metaborate[1]
Names
Other names
boric acid, lithium salt
Identifiers
3D model (JSmol)
ChemSpider
ECHA InfoCard 100.033.287
EC Number
  • 236-631-5
  • InChI=1S/BO2.Li/c2-1-3;/q-1;+1 checkY
    Key: HZRMTWQRDMYLNW-UHFFFAOYSA-N checkY
  • InChI=1/BO2.Li/c2-1-3;/q-1;+1
    Key: HZRMTWQRDMYLNW-UHFFFAOYAF
  • [Li+].[O-]B=O
Properties
LiBO2
Molar mass 49.751 g/mol
Appearance white hygroscopic monoclinic crystals
Density 2.223 g/cm3
Melting point 849 °C (1,560 °F; 1,122 K)
0.89 g/100 mL (0 °C)
2.57 g/100 mL (20 °C)
11.8 g/100 mL (80 °C)
Solubility soluble in ethanol
Thermochemistry
59.8 J/mol K
51.3 J/mol K
-1022 kJ/mol
33.9 kJ/mol
Hazards
NFPA 704 (fire diamond)
NFPA 704 four-colored diamond
2
0
0
Safety data sheet (SDS) External MSDS
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
checkY verify (what is checkY☒N ?)
Infobox references

Lithium metaborate is a chemical compound of lithium, boron, and oxygen with elemental formula LiBO2. It is often encountered as a hydrate, LiBO2·nH2O, where n is usually 2 or 4. However, these formulas do not describe the actual structure of the solids.

Lithium metaborate is one of the borates, a large family of salts (ionic compounds) with anions consisting of boron, oxygen, and hydrogen.

Structure

Lithium metaborate has several crystal forms.

The α form consists of infinite chains of trigonal planar metaborate anions [BO2O−]n.

The γ form is stable at 15 kbar and 950 °C. It has a polymeric cation consisting of a tridimensional regular array of [B(O−)4]− tetrahedra sharing oxygen vertices, alernating with lithium cations, each also surrounded by four oxygen atoms. The B-O distances are 148.3 pm, the Li-O distances are 196 pm.[2]

Lithium metaborate forms glass relatively easily, and consists of approximately 40% tetrahedral borate anions, and 60% trigonal planar boron. The ratio of tetrahedral to trigonal boron has been shown to be strongly temperature dependent in the liquid and supercooled liquid state.[3][4]

Applications

Laboratory

Fusion flux consisting of lithium metaborate and lithium teraborate, with a small amount of lithium bromide.

Molten lithium metaborate, often mixed with lithium tetraborate Li2B4O7, is used to dissolve oxide samples for analysis by XRF, AAS, ICP-OES, ICP-AES, and ICP-MS,[5] modern versions of classical bead test. The process may be used also to facilitate the dissolution of oxides in acids for wet analysis.[6] Small amounts of lithium bromide] LiBr or lithium iodide LiI may be added as mold and crucible release agents.[6]

Lithium metaborate dissolves acidic oxides MexOy with x < y, such as SiO2 Al2O3, SO3, P2O5, TiO2, Sb2O3, V2O5, WO3, and Fe2O3. Lithium tetraborate, on the other hand, dissolves basic oxides with x > y, such as CaO, MgO and other oxides of the alkali metals and alkaline earth metals. Most oxides are best dissolved in a mixture of the two lithium borate salts, for spectrochemical analysis.[6]

References

  1. ↑ David R. Lide (1998): Handbook of Chemistry and Physics, edition 87, pages 4–66. CRC Press. ISBN 0-8493-0594-2
  2. ↑ M. Marezio and J. P. Remeika (1966): "Polymorphism of LiMO2 Compounds and High‐Pressure Single‐Crystal Synthesis of LiBO2". Journal of Chemical Physics, volume 44, issue 9, pages 3348-. doi:10.1063/1.1727236
  3. ↑ Alderman, Oliver; Benmore, Chris; Weber, Rick. "Consequences of sp2–sp3 boron isomerization in supercooled liquid borates". Applied Physics Letters. 117: 131901. doi:10.1063/5.0024457.
  4. ↑ Alderman, Oliver; Benmore, Chris; Reynolds, Bryce; Royle, Brock; Feller, Steve; Weber, Rick. "Liquid fragility maximum in lithium borate glass‐forming melts related to the local structure". International Journal of Applied Glass Science. 14: 52–68. doi:10.1111/ijag.16611.
  5. ↑ Terrance D. Hettipathirana (2004): "Simultaneous determination of parts-per-million level Cr, As, Cd and Pb, and major elements in low level contaminated soils using borate fusion and energy dispersive X-ray fluorescence spectrometry with polarized excitation". Spectrochimica Acta Part B: Atomic Spectroscopy, volume 59, issue 2, pages 223-229. doi:10.1016/j.sab.2003.12.013
  6. 1 2 3 Fernand Claisse (2003): "Fusion and fluxes". Comprehensive Analytical Chemistry: Sample Preparation for Trace Element Analysis, volume 41, pages 301-311.


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