Sodium pentaborate, more properly disodium decaborate, is a chemical compound of sodium, boron, and oxygen; a salt with elemental formula NaB5O8, Na2B10O16, or Na2O·5B2O3. It is a colorless crystalline solid, soluble in water.
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Sodium pentaborate
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3D model (JSmol)
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| ECHA InfoCard | 100.031.371 |
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CompTox Dashboard (EPA)
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| Properties | |
| Na+[B5O6(OH)4]− or Na+[B5O7(OH)2]−·H2O | |
| Molar mass | 241.06 g·mol−1 |
| Appearance | Colorless crystalline solid |
| Soluble | |
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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The compound is often encountered or traded as hydrates NaB5O8·nH2O, Na2B10O16·2nH2O, or Na2O·5B2O3·2nH2O for n = 2,[1] 4,[2][3] 5,[4][5] or other values. This formula is often misleading as some of the water molecules are actually hydroxyl groups covalently attached to boron atoms.
The compound is used in agriculture as a boron supplement in fertilizer with various trade names such as Solubor[5] and Aquabor.[3] It has also been tested as an additive to improve plasma electrolytic oxidation of magnesium alloys.[4]
The name "sodium pentaborate" has also been used for a distinct compound with formula Na3B5O8·nH2O, better called trisodium pentaborate.[6]
Structure and preparation edit
Dihydrate edit
Sodium pentaborate "dihydrate" has the elemental formula NaH4B5O10, which can be parsed as NaB5O8·2H2O or Na2O·5B3O3·4H2O, however the correct formula seems to be either Na+[B5O6(OH)4]− or Na+[B5O7(OH)2]−·H2O. The latter seems more likely, since under thermogravimetric analysis the material starts to decompose at about 130 °C with partial loss of water. [1]
It can be prepared by reacting water solutions of sodium carbonate Na2CO3 and boric acid B(OH)3 in mole ratio 1:10 and evaporating the resulting solution at 40 °C. It belongs to the monoclinic crystal system with symmetry group P21/c (C2h5) and parameters a = 1110.3 pm, b = 1643.7 pm, c = 1356.4 pm, α = 89.960°, β = 112.850° and γ = 89.9°, formulas per cell Z = 4.[1]
References edit
- ^ a b c S. Stella Mary, S. Shahil Kirupavathy, P. Mythili, R. Gopalakrishnan (2008): "Growth and characterization of sodium pentaborate [Na(H4B5O10)] single crystals". Spectrochimica Acta Part A, volume 71, issue 4, 15 pages 1311-1316. doi:10.1016/j.saa.2008.04.021
- ^ M. Briggs (2001): "Boron Oxides, Boric Acid, and Borates". Chapter of the Kirk-Othmer Encyclopedia of Chemical Technology. Wiley.
- ^ a b "Aquabor 2 MSR". Product page in the Mineira Santa Rita company website. Accessed on 2022-06-27.
- ^ a b Taha Cagri Senocak, Taha Alper Yilmaz, Hasan Feyzi Budak, Gokhan Gulten, Ahmet Melik Yilmaz, Kadri Vefa Ezirmik, Yasar Totikc (2022): "Influence of sodium pentaborate (B5H10NaO13) additive in plasma electrolytic oxidation process on WE43 magnesium alloys". Materials Today Communications, volume 30, article 103157. doi:10.1016/j.mtcomm.2022.103157
- ^ a b "Solubor DF". Product page in the 20 Mule Team Borax company website. Accessed on 2022-06-27.
- ^ Silvio Menchetti and Cesare Sabelli (1977): "The crystal structure of synthetic sodium pentaborate monohydrate". Acta Crystallographica Section B, volume B33, pages 3730-3733. doi:10.1107/S0567740877011959
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