chemistry Chemistry is the science, scientific study of the properties and behavior of matter. It is a natural science that covers the Chemical element, elements that make up matter to the chemical compound, compounds made of atoms, molecules and ions ...

, tetraborate or pyroborate is an

anion An ion () is an atom or molecule with a net electrical charge. The charge of an electron is considered to be negative by convention and this charge is equal and opposite to the charge of a proton, which is considered to be positive by convent ...

(negative

ion An ion () is an atom or molecule with a net electrical charge. The charge of an electron is considered to be negative by convention and this charge is equal and opposite to the charge of a proton, which is considered to be positive by conve ...

) with formula ; or 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 ...

containing that anion, such as sodium tetraborate, . It is one of the

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 ...

oxoacid An oxyacid, oxoacid, or ternary acid is an acid that contains oxygen. Specifically, it is a compound that contains hydrogen, oxygen, and at least one other element, with at least one hydrogen atom bonded to oxygen that can dissociate to produce ...

s, that is, a

borate A borate is any of several boron oxyanions, negative ions consisting of boron and oxygen, such as orthoborate , metaborate , or tetraborate ; or any salt with such anions, such as sodium metaborate, and disodium tetraborate . The name also refe ...

. The name is also applied to the hydrated ion as present in

borax Borax is a salt (ionic compound), a hydrated borate of sodium, with chemical formula often written . It is a colorless crystalline solid, that dissolves in water to make a basic solution. It is commonly available in powder or granular form, ...

The ion occurs in

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 ...

solutions at neutral pH, being formed by condensation of

orthoborate In inorganic chemistry, an orthoborate is a polyatomic anion with formula or a salt containing the anion; such as trisodium orthoborate . It is one of several boron oxoanions, or borates. The name is also used in organic chemistry for the trival ...

and

tetrahydroxyborate Tetrahydroxyborate is an inorganic anion with the chemical formula or . It contributes no colour to tetrahydroxyborate salts. It is found in the mineral hexahydroborite, , originally formulated . It is one of the boron oxoanions, and acts as a ...

anions: : 2 B(OH)₃ + 2 ⇌ + 5 H₂O The tetraborate anion (

tetramer A tetramer () (''tetra-'', "four" + '' -mer'', "parts") is an oligomer formed from four monomers or subunits. The associated property is called ''tetramery''. An example from inorganic chemistry is titanium methoxide with the empirical formula Ti ...

) includes two tetrahedral and two trigonal boron atoms symmetrically assembled in a fused bicyclic structure. The two tetrahedral boron atoms are linked together by a common oxygen atom, and each also bears a negative net charge brought by the supplementary OH⁻ groups laterally attached to them. This intricate molecular anion also exhibits three rings: two fused distorted hexagonal (boroxole) rings and one distorted octagonal ring. Each ring is made of a succession of alternate boron and oxygen atoms. Boroxole rings are a very common structural motif in polyborate ions. The hydrated tetraborate anion occurs in the mineral

(sodium tetraborate octahydrate) with the formula Na₂ ₄O₅(OH)₄�8H₂O. The borax chemical formula is also commonly written in a more compact notation as Na₂B₄O₇·10H₂O. Sodium borate can be obtained in high purity and so can be used to make a

standard solution In analytical chemistry, a standard solution is a solution containing a precisely known concentration of an element or a substance. A known mass of solute is dissolved to make a specific volume. It is prepared using a standard substance, such as a p ...

in titrimetric analysis..

References

Anions Salts Sodium Borates {{chem-stub