Английская Википедия:Disodium octaborate
Disodium octaborate is a borate of sodium, a chemical compound of sodium, boron, and oxygen — a salt with elemental formula Шаблон:Chem2 or Шаблон:Chem2, also written as Шаблон:Chem2. It is a colorless crystalline solid, soluble in water.
Disodium octaborate is traded either as a liquid concentrate, or as the tetrahydrate Шаблон:Chem2, a white odorless powder. It is used as an insecticide,[1][2] and as a fungicide and algicide, and as a fire retardant.[3][4], and as a boron micronutrient additive in fertilizers.[5] Trade names include Bora-Care, Borathor, Termite Prufe, Board Defense, Polybor,[4] Tim-bor,[6] and Can-Bor.
Preparation
The anhydrous form can be crystallized from a molten mixture of sodium oxide Шаблон:Chem2 and boric oxide Шаблон:Chem2.[7]
Properties
Solubility
The salt dissolves in water to form forms viscous supersaturated solutions at elevated temperatures. Solubility of the tetrahydrate is 21.9% (wt) at Шаблон:Convert.[8]
Structure
The anhydrous salt exists in two stable crystalline forms, α and β.[9][10]
The α form has monoclinic crystal structure, with the P21/a space group. The unit cell parameters at 273 K are: a = 650.7 pm, b = 1779 pm, c = 837.7 pm, β = 96.6 °, Z = 4. The structure contains two interlocking boron-oxygen frameworks, each of them consisting of alternating single and double rings composed of two triangles and a tetrahedron, the so called triborate and pentaborate groups. The two frameworks are connected by two (non-equivalent) sodium atoms, each surrounded by 8 oxygens, comprising finite chains of four Шаблон:Chem2 polyhedra with shared edges. The thermal expansion is sharply anisotropic, including negative thermal expansion. The thermal expansion tensor in 273–1000 K in function of absolute temperature T has α11 = 55–0.042T, α22 = 11, α33 = -15 + 0.032T (×10–6) K–1, μ = (c^α33) = 42°.[9]
The β form has monoclinic crystal structure, with the P21/c space group. The unit cell parameters are a = 1173.1 pm, b = 788.0 pm, c = 1041.0 pm, β = 99.883 °, Z = 4. The structure consists of two infinite, independent, and interleaved boron–oxygen networks containing a complex borate anion Шаблон:Chem2 formed by six Шаблон:Chem2 triangles (Δ) and two Шаблон:Chem2 tetrahedra (T), which can be viewed as a Шаблон:Chem2 group linked to a Шаблон:Chem2 group. This fundamental building block is identical to that of the α form and of silver octaborate Шаблон:Chem2, with some subtle differences.[10]
Uses
Dilute solutions of disodium octaborate are sprayed on wood surfaces to kill termites, powder post beetles, carpenter ants, fungi and algae. The tetrahydrate is also available as pellets for embedding in structural wood. Compared to other chemicals used for these purposes, it has the advantages of lack of odor, permanent effect, and low toxicity to humans and pets.[2]
The compound was also shown to significantly reduce dust mite populations in the home when applied as a dilute solution to carpets and upholstery together with regular vacuum cleaning.[11]
Disodium octaborate, applied to the soil or foliar spray, has been shown to inhibit pests of crops such as tomato and pistachio, with no observed detrimental effects to the plants.[12][13]
Safety
Disodium octaborate is not flammable, combustible, or explosive and has low acute oral and dermal toxicity.[1] The oral 50% lethal doses (LD50) are 5.3 g/kg for guinea pig, 2g/kg for rats.[2] However, it is classified as "reproductive toxicity category 1B (presumed human reproductive toxicant)" under the EU Classification, Labelling and Packaging Regulation (CLP Regulation). The CLP hazard code and statement are "H360FD: May damage fertility. May damage the unborn child."
On 22 February 2018, the Swedish Chemicals Agency (KEMI) submitted a proposal to the European Chemicals Agency (ECHA) to list disodium borate as a Substance of Very High Concern (SVHC) under the Registration, Evaluation, Authorisation and Restriction of Chemicals (REACH) Regulation.[14]
References
- ↑ 1,0 1,1 Шаблон:Cite journal
- ↑ 2,0 2,1 2,2 "Disodium octaborate". Substance page at the National Institutes of Health - National Library of Medicine ChemDplus website. Accessed on 2022-06-28.
- ↑ B.J Brotherton Boron: Inorganic Chemistry Encyclopedia of Inorganic Chemistry (1994) Ed. R. Bruce King, John Wiley & Sons Шаблон:ISBN
- ↑ 4,0 4,1 "Polybor". Product data page at the U. S. Borax company website. Accessed on 2022-06-27.
- ↑ "Boron sodium oxide (B8Na2O13)". Substance page at the PubChem website. Accessed on 2022-06-28.
- ↑ "[1]Шаблон:Dead link". Product data page at the U. S. Borax company website. Accessed on 2022-06-27.
- ↑ C. J. Leedecke and C. G. Bergeron (1977): "Crystallisation of Na2B8O13 in Selected Na2O-B2O3 Melts". Physics and Chemistry of Glasses (UK), volume 18, issue 6, pages 116-120.
- ↑ M. Briggs (2001): "Boron Oxides, Boric Acid, and Borates". Chapter of the Kirk-Othmer Encyclopedia of Chemical Technology. Wiley.
- ↑ 9,0 9,1 Шаблон:Cite journal
- ↑ 10,0 10,1 Шаблон:Cite journal
- ↑ Шаблон:Cite journal
- ↑ H. Kavak, A. L. Tuna, and H. S. Civelek (2017): "Effects of Tarımbor (Na2B8O13.4(H2O)) fertiliser against Tuta absoluta (Meyrick) (Lepidoptera: Gelechiidae) and biochemistry and physiology of tomato plants under greenhouse conditions." Ege Üniversitesi Ziraat Fakültesi Dergisi, volume 54, issue 2, pages 157-165 (in Turkish).
- ↑ Шаблон:Cite journal
- ↑ "Proposal for Identification of a Substance of Very High Concern on the Basis of the Criteria Set Out in REACH Article 57", Swedish Chemicals Agency, 22 February 2018.
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