| Names | |
|---|---|
| Other names boric acid, lithium salt | |
| Identifiers | |
3D model (JSmol) | |
| ChemSpider |
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| ECHA InfoCard | 100.033.287 |
| EC Number |
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| Properties | |
| LiBO2 | |
| Molar mass | 49.751 g/mol |
| Appearance | whitehygroscopicmonoclinic 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 inethanol |
| Thermochemistry | |
| 59.8 J/mol K | |
Std molar entropy(S⦵298) | 51.3 J/mol K |
Std enthalpy of formation(ΔfH⦵298) | −1022 kJ/mol |
Std enthalpy of combustion(ΔcH⦵298) | 33.9 kJ/mol |
| Hazards | |
| NFPA 704 (fire diamond) | |
| Safety data sheet (SDS) | External MSDS |
Except where otherwise noted, data are given for materials in theirstandard state (at 25 °C [77 °F], 100 kPa). | |
Lithium metaborate is achemical compound oflithium,boron, andoxygen with elemental formulaLiBO2. It is often encountered as ahydrate,LiBO2·nH2O, wheren is usually 2 or 4. However, these formulas do not describe the actual structure of the solids.
Lithium metaborate is one of theborates, a large family ofsalts (ionic compounds) with anions consisting of boron, oxygen, andhydrogen.
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 15kbar and 950 °C. It has a polymeric cation consisting of a tridimensional regular array of[B(O−)4]− tetrahedra sharingoxygen vertices, alernating with lithium cations, each also surrounded by four oxygen atoms. The B-O distances are 148.3pm, 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]
Molten lithium metaborate, often mixed withlithium tetraborateLi2B4O7, is used to dissolveoxide samples for analysis byXRF,AAS,ICP-OES,ICP-AES, andICP-MS,[5] modern versions of classicalbead test. The process may be used also to facilitate the dissolution of oxides in acids forwet analysis.[6] Small amounts oflithium bromideLiBr orlithium iodideLiI may be added asmold andcruciblerelease agents.[6]
Lithium metaborate dissolvesacidic oxidesMexOy withx <y, such asSiO2,Al2O3,SO3,P2O5,TiO2,Sb2O3,V2O5,WO3, andFe2O3. Lithium tetraborate, on the other hand, dissolvesbasic oxides withx >y, such asCaO,MgO and other oxides of thealkali metals andalkaline earth metals. Most oxides are best dissolved in a mixture of the two lithium borate salts, forspectrochemical analysis.[6]
