Sodium pentaborate, more properly disodium decaborate, is a

chemical compound A chemical compound is a chemical substance composed of many identical molecules (or molecular entities) containing atoms from more than one chemical element held together by chemical bonds. A molecule consisting of atoms of only one element ...

sodium Sodium is a chemical element with the symbol Na (from Latin ''natrium'') and atomic number 11. It is a soft, silvery-white, highly reactive metal. Sodium is an alkali metal, being in group 1 of the periodic table. Its only stable iso ...

boron Boron is a chemical element with the symbol B and atomic number 5. In its crystalline form it is a brittle, dark, lustrous metalloid; in its amorphous form it is a brown powder. As the lightest element of the ''boron group'' it has th ...

, and

oxygen Oxygen is the chemical element with the symbol O and atomic number 8. It is a member of the chalcogen group in the periodic table, a highly reactive nonmetal, and an oxidizing agent that readily forms oxides with most elements as wel ...

; a

salt Salt is a mineral composed primarily of sodium chloride (NaCl), a chemical compound belonging to the larger class of salts; salt in the form of a natural crystalline mineral is known as rock salt or halite. Salt is present in vast quantitie ...

with elemental formula , , or . It is a transparent colorless crystalline solid, soluble in water. The compound is often encountered or traded as

hydrate In chemistry, a hydrate is a substance that contains water or its constituent elements. The chemical state of the water varies widely between different classes of hydrates, some of which were so labeled before their chemical structure was understo ...

s , , or for ''n'' = 2, 4, 5, or other values. This formula is often misleading as some of the water molecules are actually

hydroxyl In chemistry, a hydroxy or hydroxyl group is a functional group with the chemical formula and composed of one oxygen atom covalently bonded to one hydrogen atom. In organic chemistry, alcohols and carboxylic acids contain one or more hydroxy ...

groups

covalently A covalent bond is a chemical bond that involves the sharing of electrons to form electron pairs between atoms. These electron pairs are known as shared pairs or bonding pairs. The stable balance of attractive and repulsive forces between atoms ...

attached to boron atoms. The compound is used in

agriculture Agriculture or farming is the practice of cultivating plants and livestock. Agriculture was the key development in the rise of sedentary human civilization, whereby farming of domesticated species created food surpluses that enabled people to ...

as a boron supplement in

fertilizer A fertilizer (American English) or fertiliser (British English; see spelling differences) is any material of natural or synthetic origin that is applied to soil or to plant tissues to supply plant nutrients. Fertilizers may be distinct from ...

with various trade names such as Solubor and Aquabor. It has also been tested as an additive to improve

plasma electrolytic oxidation Plasma electrolytic oxidation (PEO), also known as electrolytic plasma oxidation (EPO) or microarc oxidation (MAO), is an electrochemical surface treatment process for generating oxide coatings on metals. It is similar to anodizing, but it emplo ...

magnesium Magnesium is a chemical element with the symbol Mg and atomic number 12. It is a shiny gray metal having a low density, low melting point and high chemical reactivity. Like the other alkaline earth metals (group 2 of the periodic ta ...

alloys. The name "sodium pentaborate" has also been used for a distinct compound with formula , better called

trisodium pentaborate Trisodium pentaborate is a salt that can form as a monohydrate with formula , which contains the anion dihydroxydopentaborate . Its formula may be incorrectly given as , or as . It may also be called simply sodium pentaborate, but this name i ...

Structure and preparation

Dihydrate

Sodium pentaborate "dihydrate" has the elemental formula , which can be parsed as or , however the correct formula seems to be either or . The latter seems more likely, since under

thermogravimetric analysis Thermogravimetric analysis or thermal gravimetric analysis (TGA) is a method of thermal analysis in which the mass of a sample is measured over time as the temperature changes. This measurement provides information about physical phenomena, such ...

the material starts to decompose at about 130 °C with partial loss of water. It can be prepared by reacting water solutions of

sodium carbonate Sodium carbonate, , (also known as washing soda, soda ash and soda crystals) is the inorganic compound with the formula Na2CO3 and its various hydrates. All forms are white, odourless, water-soluble salts that yield moderately alkaline solutions ...

and

boric acid Boric acid, more specifically orthoboric acid, is a compound of boron, oxygen, and hydrogen with formula . It may also be called hydrogen borate or boracic acid. It is usually encountered as colorless crystals or a white powder, that dissolves ...

in mole ratio 1:10 and evaporating the resulting solution at 40 °C. It belongs to the

monoclinic crystal system In crystallography, the monoclinic crystal system is one of the seven crystal systems. A crystal system is described by three vectors. In the monoclinic system, the crystal is described by vectors of unequal lengths, as in the orthorhombic sy ...

with

symmetry group In group theory, the symmetry group of a geometric object is the group of all transformations under which the object is invariant, endowed with the group operation of composition. Such a transformation is an invertible mapping of the ambient ...

''P''2₁/c (C_2h⁵) and

parameters A parameter (), generally, is any characteristic that can help in defining or classifying a particular system (meaning an event, project, object, situation, etc.). That is, a parameter is an element of a system that is useful, or critical, when ...

''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.

References

S. Stella Mary, S. Shahil Kirupavathy, P. Mythili, R. Gopalakrishnan (2008): "Growth and characterization of sodium pentaborate a(H₄B₅O₁₀)single crystals". ''Spectrochimica Acta Part A'', volume 71, issue 4, 15 pages 1311-1316. 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. Silvio Menchetti and Cesare Sabelli (1977): "The crystal structure of synthetic sodium pentaborate monohydrate". ''Acta Crystallographica Section B'', volume B33, pages 3730-3733. Solubor DF
. Product page in the ''20 Mule Team Borax'' company website. Accessed on 2022-06-27. Aquabor 2 MSR
. Product page in the ''Mineira Santa Rita'' company website. Accessed on 2022-06-27. M. Briggs (2001): "Boron Oxides, Boric Acid, and Borates". Chapter of the ''Kirk-Othmer Encyclopedia of Chemical Technology''. Wiley. Borates {{chem-stub