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Sodium pyrosilicate is the chemical compound Na
6Si
2O
7. It is one of the sodium silicates, specifically a pyrosilicate, formally a salt of the unstable pyrosilicic acid H
6Si
2O
7.[2][3]

Structure

The anhydrous solid has the triclinic crystal structure. The Si
2O6−
7 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 NaO
4 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 Å3, Z = 32).[1]

References

  1. ^ a b c 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. doi:10.1002/zaac.201000120
  2. ^ Myron C Waddell (1932): “Process of purifying technical sodium pyrosilicate hydrates”. US patent US1931364A.
  3. ^ J. F. Schairer and N. L. Bowen (1956): “The system Na
    2    O    —Al
    2    O
    3    —SiO
    2    “. American Journal of Science, volume 254, issue 3, pages 129-195 doi:10.2475/ajs.254.3.129