Sodium pyrosilicate is the
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 ele ...
. It is one of the
sodium silicates, specifically a
pyrosilicate, formally 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 quanti ...
of the unstable
pyrosilicic acid .
[Myron C Waddell (1932): "Process of purifying technical sodium pyrosilicate hydrates". US patent US1931364A.][J. F. Schairer and N. L. Bowen (1956): "The system ——". ''American Journal of Science'', volume 254, issue 3, pages 129-195 ]
Structure
The anhydrous solid has the
triclinic
180px, Triclinic (a ≠ b ≠ c and α ≠ β ≠ γ )
In crystallography, the triclinic (or anorthic) crystal system is one of the 7 crystal systems. A crystal system is described by three basis vectors. In the triclinic system, the crystal i ...
crystal structure, with space group P (a = 5.8007(8)
Å, b = 11.5811(15) Å, c = 23.157(3) Å, α = 89.709(10)°, β = 88.915(11)°, γ = 89.004(11)°, V = 1555.1(4) Å
3, Z = 8, Dx = 2.615 g·cm
−3, μ(Mo‐Kα) = 7.94 cm
−1). The anions are arranged in layers parallel to the (100) plane, with the sodium cations distributed in 24 distinct crystallographic positions, coordinated by 4 to 6 near oxygen atoms. Some of the 4-coordinated sodium atoms can be interpreted as parallel columns of edge-sharing tetrahedra. The columnar arrangement forms tunnels that house the remaining sodium cations. Twinning at a microscopic scale simulates a much larger monoclinic C centered lattice (V′ = 6220 Å
3, Z = 32).
[Volker Kahlenberg, Thomas Langreiter, and Erik Arroyabe (2010): "Na6Si2O7 – The Missing Structural Link among Alkali Pyrosilicates". ''Zeitschrift für anorganishe und allgemeine Chemie'' (''Journal for Inorganic and General Chemistry''), volume 636, issue 11, pages 1974-1979. ]
See also
*
Sodium metasilicate,
*
Sodium orthosilicate,
References
{{reflist
Sodium compounds