Disodium enneaborate is the traditional name for 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 ...
of
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 ...
,
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 ...
, and
hydrogen
Hydrogen is the chemical element with the symbol H and atomic number 1. Hydrogen is the lightest element. At standard conditions hydrogen is a gas of diatomic molecules having the formula . It is colorless, odorless, tasteless, non-toxic, an ...
, with
elemental formula or . It is the sodium borate with the highest boron/sodium ratio.
[
]
Structure
The correct formula has since been determined to be . The anion is a linear polymer with repeating unit . Sodium cations, water molecules, and undissociated 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 ...
molecules lie between the chains, held by numerous hydrogen bond
In chemistry, a hydrogen bond (or H-bond) is a primarily electrostatic force of attraction between a hydrogen (H) atom which is covalently bound to a more electronegative "donor" atom or group (Dn), and another electronegative atom bearing a ...
s.[
The compound crystallizes in 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 space group ''P''21/''n''. The cell parameters are ''a'' = 1021.3 pm, ''b'' = 1294.0 pm, ''c'' = 1245.7 pm, β = 93.070°, ''V'' = 1.6440 nm3, and ''Z'' = 2. The sodium cations occur in groups of four with interatomic distances of 378.30 pm and 379.32 pm.[
]
Reactions
Upon heating, disodium enneaborate initially becomes amorphous and then crystallizes as anhydrous disodium octaborate α- along with amorphous . Notably, the former contains octaborate fundamental building blocks that are topologically equivalent to those in the enneaborate.[
]
References
[Doinita Neiner, Yulia V. Sevryugina, Larry S. Harrower, and David M. Schubert (2017): "Structure and Properties of Sodium Enneaborate, Na2 8O11(OH)4·B(OH)3·2H2O". ''Inorganic Chemistry'', volume 56, issue 12, pages 7175–7181. ]
Borates
Sodium compounds
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